Reddit reviews M1 Garand Rifle Sling, Cotton Web, Black, w/ Parkerized Hardware

Sling
If you had more time, you could get one from the Appleseed store.

Don't forget sling swivels for a 1.25in sling, whether QD or otherwise. Front and back. You need to detach the rear mount point, so tying the sling on won't work.

I use 10 round pmags myself. Magpul does make them.

Edit: changed to cotton sling instead of nylon.