The MAG 21s were inflated using a regular looking shock pump with a dail that had a 'needle' like thing on the end the same as is used to inflate footballs etc. I would geuss the RS1s used the same system?
I would think Tim Flooks would be the best point of contact, I think Chipps mentioned in an STW article that he even still has spares for RS1s!
If your really stuck I have said pump (whereabouts uncertain), which I will cheerfully loan to you (although I think the needle thing might have broken)