I'm that that familiar with gun terminology, so I'm not exactly sure what you're looking for...
If you mean the feed chutes, zip ties might work if you could get paint to stick to them (they're either polyethylene or polypropylene; neither takes paint that well)
If you mean the exhaust chutes, I can't think of a product off the top of my head, but would probably try to make it by bending a piece of thick wire or tubing to shape, and then wrapping with 30ish gauge wire.