if you go to the EBC and SBS websites and look through their catalogues you will find sizes of shoes and what shoes are the same as what on other bikes etc. You should find your answers in there. i am pretty sure the shoes would be available from SBS or EBC or Ferodo or Bendix or someone.
I looked in the paper catalogues and
XL500RC is the same as XLR400 and is SBS #2077, size 130 x 25mm
In Bendix is #BA077 , also they say 130 x 25mm
In EBC it is #H332 , also they say 130 x 25mm
Also you can compare honda part numbers on
www.cmsnl.com This Honda cross reference programe might be handy for you too
http://www.zedder.com/msg16.htmIf you cant find shoes there is a place in Adelaide i could recommend to re fit new linings to old shoes for about $40
also the 81-83 XR250, 81-82 XR500, 81-82 CR450/480 and 81-82 CR250 have a 130mm TLS brake aswell but the shoes are slightly different.
part number for those is....
SBS 2030, 130 X 25mm
EBC H327, 130 X 30mm - yes this doesnt agree with what SBS say
Bendix BA030, 130 X 25mm
also
83 CR480/CR250 is EBC H328, 130 X 30
not listed in Bendix or SBS