Keep an eye on lowendbox.com’s hosting offers. There’s some junk to wade through, but it sounds like exactly what you’re after.

Not sure how wide a variety of sizes there are, but I’d search for “threaded inserts.” You drill the holes and screw the inserts in and that gives you an interface for machine bolts. I’ve only seen them in bigger sizes, but I wouldn’t be surprised if there are some that would fit standoffs.