I picked up a pair of mittens from here
https://www.etsy.com/shop/StraitJacketShop
I got the ones with magnet locks cause I wanted to play with them with self bondage. There's just enough give in them to pick up the key but not much else. They're cozy and keep my hands mostly useless but they're fist style mittens so my hands are balled up which can get a bit uncomfortable after a long period of time.
I also have a pair of posey mittens that I got from walmart of all places.
https://www.walmart.com/ip/Double-S...-Fits-Most-Tie-Strap-1-Strap-1-Pair/680501220
They're open hand style and your hand is pressed against a padded cushion inside them. They are secured to your wrist with velcro and you can get them on and off with some effort and your teeth.