Not sure if you know this but seitan is incredibly easy to make at home. And really inexpensive too.
Because flour absorbsion varies you'll need to adjust slightly:
2C high gluten flour
1 1/4 to 1 1/2C broth or water
and seasonings you may enjoy
mix to combine ingredients then knead for 3 minutes, let rest for 5 minutes, then knead again. Dredge in a little extra flour. Cut into pieces of desired size.
drop pieces into rapidly simmering (but not boiling) salted water or broth
when they float let cook for 3 more minutes then remove with a slotted spoon and drain. These will be very moist a dumpling like and you can eat them like this if you want. But if you want the denser, chewier texture wrap in paper towels and put a heavy weight on top to drive out the excess moisture.
From this point you can wok, stirfry, grill, broil, bake, saute, deep fry... whatever. You can even coat it in panko to make fake meat cutlets.
Sorry I couldn't help you with the restaurants, but hope you'll try making your own.