Spaenaur has (had) most styles listed in their catalogue. They are not always the cheapest, but the selection is good and many of their wares (things like weatherstrip, canvas goods, buckles, upholstery items, slot headed screws) are suitable for vintage vehicles. Their catalogue is available online in PDF format.
http://www.spaenaur.com/products.asp
I think page C51 has what you are looking for:
http://www.spaenaur.com/view_pdf.asp?Page=C51
I just noticed you are in England. Spae-nur is a Canadian company located out of Southern Ontario.