Have you ever played with superglue and various powders? I was sceptical until I did a repair job using superglue and baking soda. It sets like steel. You could use superglue and charcoal powder. Some heat and wax crayon and force may get the broken bolt out. Run a tap through, reinstall using SG &CP and then grease.
Oh yes, it's a laugh and a half, don't inhale the fumes, plastic welded my 1199 nose cone with it, laugh a minute, works tho
Look like any old (brass?) threaded inserts - nothing special. I expect a quick eBay search would be fruitful...
Yeah, gluing plastics is always tricky...for the oily stuff (HDPE etc) I've had success welding with a soldering iron. Plastic fuel cans chopped up to make the filler rod.
Yup - I meant any old moulded-in insert. I'd expect it to have a closed-off end if originally moulded in.