In our house, we have an abundance of unpaired and holey socks, many of them in black, brown, navy and tan colors. For fingerless mitts - sans thumbhole - just cut off the entire foot from the cuffs from a matching pair of socks. Voila! Wrist warmers.
If you want a thumb slot, cut the foot to just above the heel, where you can cut straight across and have the fabric even. Cut a side slit into the fabric below the cuff for the thumb to go through.
Embellish the cuff with buttons, if you please. Sew lace onto the snipped end for a longer glove and for beauty. Edge the thumb slot with blanket or ornamental stitching. And, if these wear out, it's an item you likely would have thrown out, anyway, and is easy to replace.
I might even make a pair for myself.
(image borrowed, as an example of a good Steampunk fingerless glove, from Kaboodle)