I just plugged mine up, modded the release valve to fit a small schrader valve for air input, and fed a small tire pump to that. But I'm wondering, what part of the PC tank did you bust in the repair? If you pierced the rubber tank itself,
Doom and others have some good suggestions.
If it's just one of the plastic caps, I'd suggest you just get a 1/2" CPVC endcap, use an exacto or curved hobby knife blade to score little ridges in the pre-smoothed side (if the side has ridge designs or something silly like that), facing open to the direction pressure would force it out (you know, the intelligent way), toss on some duct tape (vain attempt to prevent metal cutting into the rubber), then hose clamp the sucker. If it's the end with the two tubes feeding out, drill two holes about 7/16" or smaller, feed in some 1/4" OD flexible PVC tubing (vinyl, whatever), and Goop it all in. Same goes for the connections to the trigger and pump. I have this going on my Wildfire due to a splintered forward/air release clamp, and it works just fine assuming you don't nuke it with more pressure than the initial release valve would take.
If it's just the tubing, replace it with 1/4" OD flexible PVC [Vinyl] tubing, and Goop or epoxy it in.
Don't give up yet!
Meanwhile Alex, you used the O-rings to ensure proper sealing on both sides, or in some other intricate way? My understanding of pressure would place those O-rings centrally as filler with any applicable repair for that type of break, so I'm not sure of your application.