How does my CA corporation sue a NY corporation for non-payment for services?

3 separate invoices ($8K, $5K & $200) were approved for payment by the CEO of One Day University. Our corporation provided marketing & advertising services to them on the basis of a signed estimate. After the invoices had been approved, but before the checks were cut, The Learning Annex bought One Day University. The terms of the transaction stipulated The Learning Annex would assume ODU's debt. The Learning Annex delayed payment, but never denied its responsibility, until CEO Bill Zanker finally sent a brief email saying he would offer 23 cents on the dollar, take it or leave it. The Learning Annex has a well-documented history of non-payment. This is too much money for us to walk away from. We are prohibited from filing in our county's Small Claims Court because The Learning Annex no longer has a CA representative to receive the summons. We cannot file in NY Small Claims Court because our HQ is in CA. What are our options?