First off, what pistol? I can almost guarantee that you're not looking hard enough. If it's true, Trigger Airsoft allows for special orders. It is worth shooting them an email.
Secondly, I've bought a few GBB guns from the states. As long as they state the FPS and it's over 366 they will let them in. Some websites even adjust and chrono the guns so they become legal for crossing. Mine were never tested, but they were opened.