Even better then thermal paste + super glue is Arctic Silver Thermal Adhesive, it's as it name implies a thermal paste that harden as glue and stick the heatsink on there with thermal paste properties, I use it as a mad man on many things since it works great.
A knife and some tinkering to get the heatsink of if you ever want and then just acetone to clean the heatsink/CPU from the thermal adhesive off


Ive used this for quite heavy coolers on x86 PC's to fit CPU coolers that where for different sockets and it works like a charm!
Ive also used this for all things I want to put heatsinks on that has no mounting holes like vRAM, mosfets etc