Dude, run your spell checker.
Well no way would instant metal be worth trying. It has no real tensile strength.
However if you got desperate you could totally disassemble the cylinder, removing the seals & piston & then get it ally welded by a competent welder, not just a mate. If they can keep enough heat out of the rest of it, it won’t distort the bore. Has worked ok before now.
Must be cleaned thoroughly after & the time you pay to get someone to disassemble/assemble it may not be worth it if you can’t do it yourself.
If your cylinder has a little window this will need to be pushed out & glued in later with epoxy.