The Jim Clark Trust is a charitable trust set up, in their words, to -
promote the inspiration and legacy of double F1 World Champion and Indianapolis 500 winner Jim Clark.
I saw some of their merchandise on their Facebook site - 'The Jim Clark Trust'. I have attached a copy of their catalog of items for sale, as of 12/4/19. I have a JCT cap, and have ordered a jacket. They say there is still time to order for Christmas!
One word of caution; these guys do not take credits cards - you have to do an international funds transfer. Took me about 10 minutes to set up from my bank account, and didn't cost me anything for the money exchange.