I have used plumbing pipe stops like this one:
https://www.zoro.com/cherne-industri...27/i/G0254423/
Mixed results, the first couple of times I used them they worked great. The most recent time it seemed like they had made the rubber softer and I ended up using (2) 2" rubber stops and stuffed (1) 1.5" stopper inside of each 2" rubber stop and they mimic the 60d bumpers rather well. They are black and don't look as cool as the original yellow bumpers, but they work.
Cheaper than the $54 they want for them here:
https://www.suspensionforkparts.net/....html?page=all
Cheers,
-Mike