In reply to Csimp1:
I've certainly had custom kit from Lowe Alpine and Mountain Equipment before, but I didn't have anything to do with sourcing it.
Otherwise, just get a load of sale kit from somewhere and take it to be embroidered/printed - I've done this before, but many years ago, so can't be more help for anyone current.
T-shirts and fleeces are easy, but any embroidery on a softshell will knacker it.