Make up a name and register. Most companies won't check.
Check out Buytshirts online https://www.buytshirtsonline.co.uk/ for small quantities with no account.

There is a seller on ebay that I occasionaly use, Powcog, if I want single pieces/samples outside of my usual buying schedule. Not quite trade prices but free postage often makes them cheaper than buying a few pieces from a wholesaler.