You probably aren't going to find any newer cards that work with drivers that support advanced tools like AirSnort. I would recommend getting a card through eBay.
The Senao SL-2511CD PLUS EXT2 uses the Prism2.5 chipset and has a maximum output of 250mW. It also requires an external antenna. So that seems to be a decent choice. You can get one e.g. here:
http://cgi.ebay.com/ws/eBayISAPI.dll...ayphotohosting
(actually that's a 200mW Senao NL-2511CD but it does have two MMCX connectors, so it's good)
Now that I check the AirSnort site, they only say Prism2 cards, so I don't know if the Prism2.5 would work.
But they do support Cisco Aironet cards, and those are decent (I've got one). Try the Cisco AIR-LMC352, it's the Aironet 350 PC-Card with two MMCX connectors.
It's a tad expensive, though:
http://www.thenerds.net/productpage.asp?un=149036&s=1
http://www.nextag.com/serv/main/buye...co_aironet_350