If all else fails, you could try using Plastex to rebuild the broken part Plastex, there is a little bit of a learning curve with it but I have used it very successfully to repair things.
I take it you mean the plastic stand-offs which the screws screw into?
If so, get some cheap clear two pack epoxy glue from such as Wilko's and stick them back with that.
Mix up a small amount and lightly coat both sides, now carefully place broken part into position, making sure it fits perfectly back into place, hold in place with and elastic band until set, done dozens and this is an 100% successful fix.
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