Benjamin Benjamin 422 Feeding Issue

I know the reason these pistols were unsuccessful in the marketplace and discontinued is how the "magazine" worked, with three #009 O-rings somewhat controlling the feeding forward of the pellets to the firing position. I haven't looked into how to replace said O-rings, but the 422 pistol I have suffers from multiple feeds. It was a gun my grand-dad had, and as I recall he acquired it from a co-worker in pieces in a coffee can. He then sent it off to Benjamin, and the returned it fully functioning in original packaging. I remember shooting it in the late 70s or early 80s and it functioned well with no, or very few, double feeds occurring back then. Now double-feeds are the norm. If anyone has any suggestions about how to go about replacing the o-rings, or someone who does this work, I'd greatly appreciate hearing them.