I'm not a cannoli expert by any means; I've only had them a couple of times, so I have few points of reference. Nevertheless, both my wife & I like the ones at Porta Via in Pasadena. They fill the shells to order, so they're not sitting around all day getting soggy; I imagine they might be willing to give you the shell & filling separately.
Porta Via Italian Foods
1 W California Blvd, Pasadena, CA 91105