LH seal is same as RS250NX5, so order from any Honda dealer and it should be easy to get. It's also used on NSR400

RH seal is very likely discontinued, but it'll be worth having a look around. I would suspect that the later mdel MC21/28 seal would work though as it's internal and outside diameters are the same. Only the thickness is different.

You need to do a leakdown test to check condition of seals. If they leak replace them, if they don't, then it'll be worth replacing them anyway 'cos if the motor's never been apart that means they've been in there for 18 years!