Not really feasible as the guts of the action that index the magazine are on the left under a plate and cocking lever on right side. When I shoot anything on bag, easy enough to cock right handed. For lefty offhand I have my full lefty Rapid. I'm a left eye dominant shooter though I much prefer ambidextrous stocks & universal cocking.
If you want anything done to a Rainstorm or any other Korean airgun, Will Piatt of Saddle Mountain Gunsmith is the "go to" man for anything that can or need be done to them. I had 4 Rainstorm rifles and 2 Sumatras. One RS had a very nice QD FF addition made by Will. Was $175 at the time. Last I heard now $125.00. If it could be done Will is who you want to talk to.