Don't know about where to buy chistorra here offhand, but I have ordered meats through latienda.com with no issues (one time, the morcilla with rice, it was exactly what I was looking for). Chistorra is more of a seasonal (winter) food where I lived, so I know of it but only had it once. Chorizo is what they cure and have around for the summer, morcilla with rice is made fresh weekly. The quick-curing stuff like chistorra supposedly doesn't work right (or at least doesn't "seem" right to the Cantabricos) when it's hot.
El Mercado next to Tango Sur has a good pipeline to suppliers in the Americas and at least one in Spain. You can give them a holler and see what they have to say:
3767 N Southport Avenue (between Grace St & Waveland Ave) Chicago, IL 60613. (773) 477-5020
Final thought would be the guys at Juicy Wine Company. They probably don't have it but will know exactly who to get it from.