Having come across many a broken clip on Mac cases, a quick rundown of my efforts:
- CA glue - no good on small clips but good for large long chunks (eg. broken bezels with long seam can be repaired without much visible damage). CA glue + baking soda allows you to strengthen the bond but can get messy and is only good for clips you don't see.
- JB Weld - good in some instances, again for clips you don't see owing to colour, use to stabilise areas around clips. JB Weld + 3D printed brackets are next level, eg PowerBook lugs and hinges
- ABS cement - yet to dry, have heard that shavings of same plastic + put overnight in small jar of acetone to make a glue is very effective
- Good quality epoxy such as the stuff that dries clear (Gorilla brand) - has some flex, good for large clips with glue stabilising the side you can't see
Another thing to try is before you glue the clip back on, to shave down the clip a mm or two so it doesn't need to flex as much when removing the part - using a razor or scalpel. This works great for repaired clips such as the ones that breaks on 6100 cases etc.