For a vendor in the USA, I recommend J & L Orchids, they currently do not have Masd. erinacea listed, but they have had it in the past. You can trust them for mail order, I have bought from them occasionally
http://www.jlorchids.com/
The only source I checked that had Masd erinacea listed was Colombian Orchid Imports. They have a commercial growing range in Colombia. They bring in 3 or 4 shipments a year from Colombia. The way it works, you send in your order, when they have sufficient orders to make the import permits, inspection, expediting service and such cost effective, they bring a shipment into the USA. your order then gets shipped from their USA based greenhouse. They currently do have Masdevallia erinacea on their list. Contact them to see if you can get some.
http://www.colombianorchidimports.com/ I have not ordered from them, but they have a good reputation.
Another importer I would check out would be Ecuagenera. They attend several shows every year in the USA. place your order via email, then either pick the order up at an orchid show they are attending or they will mail your order to you from the show venue.
http://www.ecuagenera.com/ORCHID-SPECIES
Basically, this is all I have at the moment for sources. By the way, Masdevallia erinacea is not common in the USA because it is not easy to grow. This is not a beginners plant, in fact I can not tell you how to grow it, as I killed mine a number of years ago. But if you have grown other Masdevallias, and have had good results I think it could work for you.
Second suggestion. In the USA, it is easier to get imported plants to establish if you import them in spring, rather than autumn. I would contact the vendors, reserve your plant but ask them to hold it until the spring shipment. You will have a better chance of the plant surviving.
Hope this helps.