Your best place to pick up a C15 is on e-bay. They show up about once a month at least and are usually less than $20 US.

In fact, I just checked and there are two currently listed...
http://cgi.ebay.com/ws/eBayISAPI.dll...&category=2588
http://cgi.ebay.com/ws/eBayISAPI.dll...&category=2589

The Tamiya FAT is not well made. It doesn't fit together well at all, so keep this in mind.