Find a Class III dealer in your area, and go talk to them. Usually you will get a better response in person than over the phone.
They are available, and the prices seem to have begun a slight shift toward the less expensive. Funny thing, as the sales of semi-automatic firearms have increased, with their prices the..... prices of the full auto stuff has trended downward by a very small margin.
It is always better to have you base knowledge in place as well as a plan on how you will be acquiring your product when you talk to the dealer. Those guys seem to spend a lot of their time explaining to shoppers what the requirements are, and seem to be more appreciative of those who have the knowledge already, and know which path they will use to buy the item.
Good Luck,