I would not be too worried about not having any spares. I got three boxes of spares with my RS. 99% of them were fit for nothing but the bucket!
Some jets /needles would be nice but they are easy to get a hold off.
When I bought my RS I was promised set up data etc. Funnily enough that never appeared. The sum total of info I received for my RS was that it run on Avgas. When I asked if it was actually set up for Avgas I got no reply...
At the end of the day, it is 14 year old race bike and it will show. There will have been things done/bodged on that bike that will make you cry!
Anyway, enough of the boring stuff and do as I did. Buy it, spend a fortune on it and worry about the finer details if / when you actually start riding the bike.

P.S.
Re: Spare parts. After you have spent a fortune on your RS you will have plenty of spare parts left over...

P.P.S. I'm not trying to put you off or sound like a smart a** but those Spondon swingarms look gash in my opinion.