the trouble with an actual lawsuit is that, as I understand it, you
have to file where THEY are.
Not necessarily. This is what lawyers call Minimal Contact. A State
court can have jurisdiction over out of state party, if such party
has a minimal contact with the state. So if this gallery does
business with some other artists in your area, or even have been
doing business with you for some time, or have any other kind of
business relationship with your state. Sometimes even having a
vacation home in your state is enough for your state court to
acquire jurisdiction over them and allow you to sue in your state.
Another option is Federal Court. Federal court requires contracts to
have some minimal value. At present it may be around $70,000, I am
not sure. You can overcome this by suing for additional things to
get to the magic number. Law does not require you to be awarded this
number, only to file a lawsuit.
Sometimes, contract disputes can be framed as violation of Criminal
Statutes. If contact negotiations involved Post Office and
non-compliance was planned, it could be a Mail Fraud, which
incorporates other fraudulent activities.
Do not take it as legal advice, since I am not a lawyer. I am sure
that competent attorney should be able to construct several other
avenues of attack. The main point is, if you deal with scum, go all
the way and wipe the scum from the face of the planet Earth.