Ring Compressor?

[snydes]

Looking for a ring compressor that completely comes apart so I can put my pistons back in.

[Evilchicken0]

You should be able to do it without a compressor. Lock the pistons with some timber battens under higher piston skirts. Push the rings into the slots opposite the pegs then squeeze the rings and feed the barrels onto them ... the weight of the barrels will help tap it once with your rubber mallet. Then do the other side.
If they don't go in smoothly check the oil rings, the corrugated ring can overlap itself and jamb in the mouth of the barrel. If it's all ok it will work, if something's wrong it won't .... so if it doesn't you need to check the rings are in the right place
Growing an extra arm will help but failing that get somebody to help holding the barrels and then tapping the barrels on.