For those considering replacing their engine mounts, searching on the Facebook Yanmar 2GM group, there are a few suppliers that are mentioned.
Ellenbogen – this fellow is very active on the Facebook group and users report him to be very helpful with installation support post-purchase.
Polyflex lists their Canadian distributor as Gartside Marine – these are widely recommended on user forums.
PYI Inc. supplies R&D engine mounts. PYI are the makers of the most popular PSS Shaft Seal and have a good reputation.
Isoflex is another manufacturer of after market mounts