The folks at http://www.mecoa.com are closing out their remaining GMS engine inventory right now, and they have some pretty good deals. You can buy 3 of the GMS .47 engines for $169.99 after coupon code (GMS2007). You can buy 2 of the GMS 1.20 engines for $189.99 after coupon code. They also have a deal where you can get a GMS .40, a GMS .47, and a GMS 1.20 all for $189.99.

My experience with the GMS .47 was very positive, and I wouldn't hesitate to buy another one of these engines for the right project.