I went to Berkeley Farmer's Market on Saturday to buy vegetables and came across this stall.
The ppl there were very nice and clearly answered all my questions because I am not a sausage expert. We finally settled on the crepinettes. They came in a package of two for $6 (about 5-6 oz per crepinette).
I had these the next night for dinner. Wonderful, wonderful, wonderful. The duck liver was just enough to add some richness to the patty, but not so much that it overwhelmed the pork. If there other items are as good as these crepinettes, I will be a customer for a long time.