Mine aren't chewers but here are the guidelines as I understand them:
1) NO glow-in-the-dark ANYTHING.
2) NOTHING metallic (because it can flake off and can harm your suggies).
3) Use non-toxic craft lace (my favorite brand is Rexlace).
4) Plastic toys, like those for toddlers (i.e. Fisher Price, Link N Learn Links aka "C Links") should be fine. I guess they're designed for human chewers, too?
5) Don't use anything bead smaller in diameter than a pony bead.
I don't think they would try to swallow anything as large as a pony bead but like I said, I don't have chewers. I imagine they would try to chew on it first, and when they don't break down, they give up? As a human, I wouldn't try to swallow an avocado pit. I imagine that's how they perceive it, but Idk.
I suppose certain plastics like rubber duckies were made so that if one's dog were to chew and swallow them, they would not be poisoned. Also, Idk...I DO know from being on the forums that if they do chew and swallow, they just poop it out and all is well.
But I got lucky: no chewers.
Which means I get to make toys and save money because they are not destroyed in days!