We have an English market in San Diego that I get black pudding and a few other things from on occasion.

Amazon carries a lot of non perishable items as well (think branston pickle or suet).

Learning to make your own British food isn’t too difficult with YouTube now. We’ve been making Cumberland pie recently because our preferred grocer has started carrying ground lamb. I’ve considered making my own black pudding if I can find a good source of blood (I think the Asian markets may have it).