Zip ties is a common temporary fix. Use decent sized, you'll need 2x for 1 pin replacement. Remove the busted pin, shove a zip tie through the heatsink and mobo, use the 2nd zip tie on the shaft sticking out the back and snug it decently tight. Then lock the opposite pin first, then the remaining diagonal 2. If you didn't struggle to get that first pin locked, the zip tie wasn't tight enough. When fixing permanently, reverse the procedure, 2x pins first, then opposite, then zip tie.
If all 4x pins are busted, use 8x zip ties, but don't tighten fully in 1 shot, tighten slightly in an X pattern until all 4 are really tight. Doing 1 at a time will lead to problems with paste thickness and can mess up the cpu underneath.