I will buy new or decent used conditioned ones. need 4 (2 front 2 rear)...
I once new someone, who new a guy, who legend has it, was so rich, he was able to buy an ALL NEW set of Yanmar 2GM20F engine mounts.
I try to watch mine like a hawk, keep them in sterile condition, and after 14 years and 1800 hours, are still solid and holding the alignment. I have adjusted a small amount upwards a few times over the years (one nut flat at a time) but nothing serious. The transmission flange and prop flange are slightly different diameters so radial alignment is done by feel as well as gently engaging the raised boss on the transmission side face to the depression on the prop flange face. Angular alignment has only changed slightly (0.002") once to date.
The only major alignment was done one year after buying the boat new and that was waaaaaaaay out both radially and angularly. Mind you, if you consider that the alignment was done before the boat ever saw water, it's a wonder the two flanges were even in the same compartment.
Speaking as a master of hindsight, I would think this is something that EVERY new boat should have done within the first year because the alignment is probably out by a mile.