Morning Dave,
Welcome to the mad house! Off topic and wandering topics often, so enjoy a gentle ramble through the forum, as and when.
Now for your query. Fowlers parts website is a very useful search for obscure parts and possible other bike models that might use the same parts, so here is the link:
Fowlers_Parts_BristolI searched their parts list and it came back as unobtainium
and with a last listed price of £41-72!
This sort of rampant inflation has started to afflict old OME Yamaha SRX parts recently and doesn't look like abating.
Is it #23 on the parts diagram of the frame that I have attached to this post?
Another source for parts is the Japanese auction site 'Jauce'. Yet again this is not cheap and the final cost of a part may be 3 times the bid price, once commission, import fees and P&P have been paid. However, in all my dealings the Japanese have delivered what they say they are selling, in often better condition than advertised and there still appears to be a good supply of either OME or Japanese after market "goodies".
Link to 'Jauce' and a Yamaha SRX search:
Jauce_SRX600_search Hopefully you get some pictures! Recently my computer has only produced machine symbols where a picture and lot details would normally sit, so I hope that you have better luck than me!
If you would care to send me a "Personal Message" (PM) via the forum, with your email address; I will send a SRX600 twin shock manual to your email address.
Hope this helps get the old bird back out on the road.
Good health, Bill