I deal in military blazer badges and get all my supplies from Pakistan (as do the MOD these days). I would Google "regimental tie manufacturers Pakistan" and contact one or two of the many suppliers that come up. I'd be very surprised if one of them could not do you a one-off tie at no great cost - all they have to do is modify any of the other patterns with the single brevet. May cost you a bit more, but probably no more than a fancy outfitter in the UK would charge you.