In the meantime try a cordless drill holster from Home Depot etc.
I had a slabside MKII for a while, first bullseye gun and it was incredibly accurate.
Try some CCI std velocity ammo and see if your groups improve. Should be fine for hunting at 25 yd, 40 gr bullet has some oomph.
I had a Ruger Mk II exactly like yours. Experimented with various scopes and dots, eventually settled on J Point. Extremely accurate, fun to hunt squirrels with. Like many guns I have owned, traded it off for something else. Wish I had kept that one. Great idea on the drill holster. Before I mounted the J Point, I always carried my Ruger in a fanny pack oriented to the front.