I'm pretty sure "Who North America" carries (or carried) them:
http://www.whona.com . They are an excellent store and Keith Bradbury there provides excellent service.
However, I got mine through eBay from someone in England. It just seemed the most expedient way, and I was worried that they were selling out. In the end, it cost me about $120, but it was worth it. It's a really nice, imposing piece, and the RC is a lot of fun. Scares the hell out of my cats!!
Edit: Okay, looks like they're sold out. I hunted down where it's listed (doesn't come up in searches). They do have the darker "claw" version in stock.
The only other place I can think of (other than eBay) is
http://www.doctorwhostore.com/ . I think I bought a Product Enterprises Space:1999 Eagle from them a few years back, but I'm not sure, so won't vouch for them.