The only place I've found that lists the exact part is here:
http://generatorguru.com/engine-mounts- ... -77384440/
They are expensive ($45/set plus shipping), not in stock, and just as cheesy as the busted originals.

Here's how they mount to the generator:

Looking at the photos, all four are the same, and the way the rubber is offset would make it easy to just cut out the old rubber and drill the brackets for a generic industrial replacement vibration isolator, like this:
http://www.amazon.com/JW-Winco-351-3-51 ... P5RS664M9Y
I can get a set of those for $28. (could probably get them cheaper somewhere, but pay more for shipping)
Anybody got any thoughts on this?