Reddit reviews Uxcell USB to 5.5 mm/2.1 mm 5 Volt DC Barrel Jack Power Cable (D132) (53832-A-5337

Sure! The strip I bought came with a 5.5mm female barrel plug pre-attached, and requires 12 volts. The LED strip company sells 12v adapters, but I already had one from an old external hard drive, at least while I was testing out the LEDs.

A PSU's molex connector has 4 lines: 12v, ground, ground, and 5v (yellow black black red). I used an old molex to sata adapter that I had since stripped the sata connectors from (thanks Will Urbina and monoprice), and spliced it with this USB to barrel adapter (although I probably should have gotten this adapter had I known it existed).

There's also this switch in place so I can turn the lights off for bed or whatever. Unfortunately the cables come up to the accessory PCI bracket so I may cut a hole for it down low next to the PSU if I can find the courage to damage the case. Or just paint the bracket white like Lavins said. The switch has an LED, which is why there are 3 prongs, and the negative wire that comes off of that goes to the second ground wire on the molex adapter.

Let me know if you need more detail.

Alternatively you could try this:
http://www.amazon.com/Generic-Volt-Barrel-Power-Cable/dp/B00304DZ7I/ref=pd_bxgy_e_img_y

I am planning on giving this a try, I want build something portable as well.

Or maybe just buy a smaller ac to DC converter, maybe one that is USB into a wall wart

Something like [this] (https://www.amazon.com/dp/B00304DZ7I/ref=cm_sw_r_cp_apa_E1KPAbF1BXK4G) + something like this low profile plug (except obviously one for your country)

you can use it with a good USB charger and an adapter like https://www.amazon.com/Generic-Barrel-Power-Cable-53832/dp/B00304DZ7I - I recommend using basically any charger that came with your phone, as those are usually quality. The cheap ones in the jars at checkout counters at drug stores and convenience stores are not quality.

If you buy a power supply that isn't USB, I really don't recommend cheap no-name brands. Get one from an electronics supply company... www.mouser.com or www.jameco.com are good choices.

5.5mm x 2.1mm is the most common connector size and most modern supplies are center positive.

You can go higher in current (because it will only draw what it needs - current is a maximum capability for a constant-voltage power supply which is what we are talking about here) but not in voltage. (Constant-current power supplies also exist, but those are not general-purpose items.)

It's powered by a DC barrel connector that draws 5v / 3A. If you have wall outlet that can supply 3A, which I doubt this board actually needs 3A, you can use one of these:

https://www.amazon.com/Generic-Volt-Barrel-Power-Cable/dp/B00304DZ7I

There are really only four things you have to watch for when choosing a power adapter: connector size, voltage, current, and polarity.
Input voltage is what the device in question needs to function; your headphone transmitter for example. Output voltage refers to a device, often a power supply, that delivers or sends out a certain amount of power; the thing you don't have for example.

For polarity, the same rule will almost always apply in the same way for all electronics. Yours is no exception since the pictured symbol indicates that the center pin is positive (+) and outer case is negative (-).

For voltage, 4.5v power adapters are fairly uncommon in my experience. Since your device is battery powered, it will almost certainly be able to accept an extra 0.5v on its input. 5v power adapters are also a lot cheaper and more readily available. You might even already own one.

For current, all you ever have to check is if your power adapter has an equal or greater current capacity (mA, A, milliamps, or Amps) then what the device requires. since your device is a simple headphone/audio transmitter, I'm going to guess it dosn't require much current. Maybe 500mA at the most. With that being said, 5v 2000mA power adapters are still as cheap or cheaper then most of the lesser powerful ones.

I'm going to take a wild guess and say that the jack pictured is a 2.1mm (pin) by 5.5mm (outer sleeve). This is among the most common sizes and seems to scale to your picture nicely.

In conclusion, here is what I would get:
5V DC Wall Power Adapter ($7.29 + Free Shipping)
If on a budget, this should do just as well (though might take couple weeks to ship):
Generic USB Barrel Jack Cable ($1.71 + Free Shipping)

its a usb to 5mm Dc coaxial power connector.

$1.95 w free shipping on Amazon

What about these USB to barrel jack plugs: http://www.amazon.com/Generic-Volt-Barrel-Power-Cable/dp/B00304DZ7I

Are they powerful enough? Thanks again.

I take it that it's the usual DIY Rift screen? You may be able to power as the screen's datasheet says IIRC 3.3v to 12v. You could use something like this.