Paul,
I have a set from a CB900F which are the same as the RB1 except they fit 35mm forks and a set from a CB900C which are for 37mm forks but the are taller and have a different fixing around the headlight bracket. You are welcome to borrow either or both, you even be able to help me by enlarging my 900F brackets to fit 37mm forks.
Regards
Trev