This might be a good place to look- Bayleaf on Pearl, near the Wells Fargo/across from Peppercorn in Boulder has a back room with a LOT of Brit products. All kinds of things like Spotted Dick, etc. Might call them and see.
Nora the only place I know is the English tea cup in aurora on haven and jewel it a lovely place but a bit pricey I buy mine on line sometimes I get it cheaper there ...I will be making Parkin this weekend can't wait !!! Hope this helps