Colorado,

Believe me, if I can find these things here, you can find them in US too!!!

Anyway, my solution for this sort of parts have been to cut and form from steel blocks and other parts. Many of them I got from tooling manufacturers that I work with. They are plastic injection mold builders, so they usually have an assortment of steel parts that can be machined to fit the project.

For ribs, steel tubing is a solution, you just have to cut and fit them. My gun has not been regulated yet, so I have not installed the top and botton ribs so far. But honestly I don't anticipate any serious problems in doing that.

Fred