I'll be nice as you've been so polite but this should be on the message board unless it's a direct request for a specific part, if Andy's in a good mood he'll move it.

Best source for how they should look is definately Jamie's site which appears to be off line right now.
You can find them all on here as well, the best place is probably the "front page" of the parts manual, click "Honda NSR250 parts manual", then "1990-1993" and there they all are, you can also find the part numbers of anything that is or should be on the bike here

To ID the model you can work it out from the history, so if it's a real SP from 1990 it would have been in Cabin Racing colours, it should therefore have gold magtek wheels and the number NSR250R8L on a sticker under the number plate.

If I'm right and it's a 1990 Cabin Racing '21 SP this;

is how it would have looked.

If it's an SP it should have a dry clutch (mesh clutch cover on the right hand side of the engine, and a nice rattle when you pull the clutch lever in), full adjustable forks, a remote reservoir for the (once again fully adjustable) rear shock (bolted to the frame near the kickstart) and Magtek wheels (which have Magtek embossed on one of the spokes).

Chambers turn up now and then, here and on ebay but they're only £70 a side brand new from Dave Silver Spares if you want o.e. ones.
For forks is just a matter of asking or keeping your eyes out on here, ebay etc. or Yahoo Japan Auctions if you get desperate but you'll either have to deal via a third party like Ok!shon or find a friend in Japan.
You could just find the part numbers from this site and ask at a Honda dealer what they'll cost, they can all get any part.

And welcome, when you get it post some pics, if you can't host them you can email them to me at fontyyy@dsl.pipex.com and I'll host them and mail back the board code for a gallery
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Please do not PM me technical questions, if you can't find it on the Forum start a thread