Nextel never had the 7250(CDMA); they used the 7520(IDEN). 7520's should be easy to track down on eBay. Other than that, you're stuck with the 7100i till they stop carrying that too. Or switch to Sprint and lose the PTT or switch to another provider.
I'm with Telus in Canada and they're in the process of dropping both the 7520 and the 7250.
Apparently RIM can't be bothered with what they see as a dying technology.