There's a place in Peckham (SE London) called something like "The Cardinal Cap Company" which will refurbish - primarily by fitting with new peak - SD caps.
They claim that they actually make the caps for a well-known Saville Row military tailor - when I had one of mine done, the slightly dodgy looking character (well it was Peckham) that took my cap looked under the sweatband and said "Si si, thisa isa one of ours!" (he was Italian).
I'll try and dig out a contact.
Edited to add:
Backfrom Iraq
check PMs for contact details
Teeters