Here's a couple that I saw months back:
http://www.clearercom.com/index.htm
http://www.firefoxtech.com/products/paintball/
The first one I contacted to see about getting some demo/samples for free because I work on a corporate level for one of the major wireless telecom companies. And if it worked out, I could've made some phone calls to see about carrying them in all of our retail stores throughout the country. Dealt with some guy that just dropped the ball on their end. I guess he was more worried about his ten-sy quota's over the longer term possibility of being a major distributor to the company I work for.
As far as what I've researched the idea is great. The ones carried by clearercom is made by Iasus, some Taiwan company.
http://iasus-concepts.com/noise_terminator/nt2_new/nt2r2.html
The retailer ClearerCom is located in Canada, I think. If you do get a set, let us know how it works for you.
Funniest thing is I believe ClearerCom is some mom & pop garage operation. Their site is not that bad, but there are some inconsistancies once you click around. And for the NT GP model they've posted a reveiw by someone at Helmet Harbor with a link to Helmet Harbor. HH sells the product too, so they've essentially are supporting their competitors!