Hello, If you're still looking, I found a solution. I, like you, have searched for months for a solution. Every other rubber bushing on the GS300 is offered by the aftermarket, but not this one. The reason being this is not a rubber bushing. It's what's called a pillow bushing( or rose joint in England), similar to a small ball joint. There are a few racing websites that offer replacements but they're very expensive. I found this on the British Ebay site;
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...em=190375903825
I called him this morning and he's very knowledgable about these bushings. His is nylon and outlasts the original by far. I'm going to order some today.