Reddit reviews Wheels Manufacturing 25.4-31.8 Handlebar Shim, 1 Pair

These bars should work with your old components. It's much cheaper to buy new bars than it it is to buy a new brake levers and shifters.

Edit: saw the stem has a 31.8 clamp diamater. Get a shim to.

Surly is one of the retro touring brands that still uses 25.4 stems on some of the bikes. Bars made of chromoly steel there's less/no advantage to larger 31.8 clamp

Just had a thought though, you can buy a shim for it so it will work with your current stem like this:

https://www.amazon.com/Wheels-Manufacturing-25-4-31-8-Handlebar-Shim/dp/B000AO5FME

well for your situation, you could always use a handlebar shim to make your 25.4 handlebars work with your current stem. That'd be the cheapest option. I currently have this stem on my bike and have been happy with it.

This is pretty much all you need.

https://www.amazon.com/Wheels-Manufacturing-25-4-31-8-Handlebar-Shim/dp/B000AO5FME

You can use them together with a shim: https://www.amazon.com/Wheels-Manufacturing-25-4-31-8-Handlebar-Shim/dp/B000AO5FME

You could make such a shim yourself if you have the raw materials around. Brass or soft aluminum would be easy.