Could somebody out there help me out?

I need to replace my worn out disks on my 21 [276mm] at some point but seem unable to locate a supplier. So i was thinking of going for the later type [296mm available as after market]] and using adapters on the calipers rather than trying to get hold of different fork legs i.e. MC28.

So my question is does any body currently use adapters and if so could i be cheeky and get some dimensions to make my own or has anybody got another suggestion?
_________________
MC21 300
Aprilia RS250 track bike