Hi,
not what you want to hear, but have you considered re-winding it ? Either on the same or a similar former. If you're very lucky, the primary winding might be the outer one, or a separate former ? (can't find my photos ATM). If you don't feel like counting turns, and if you still have your friend's T3 you could determine the turns ratio. Not a magnetics pro here but I assume with turns ratio, inductance, operating frequency and guestimating the current loads (should be fairly low) you can probably get pretty close ?
Chris
fenugrec