Just thought I'd update this thread to say that I ended up drilling out the broken check valve hole and gluing in some sturdy vacuum line, per the suggestions up-thread. Went slow, was careful to remove all the plastic that I drilled out. It's doing the trick for now, no delay in the fuel shut-off, etc. I decided that chasing down a more complex replacement or expensive part isn't worth the effort until I go over the rest of the vehicle and make sure it won't need major repairs after sitting for a long time. Thanks everyone for your suggestions.