I usually get them 10 at a time. Looks like the price went up to $26 :(
You can always try your luck on ebay. Looks like lots of vendors are shipping new ones from HK.
The '02 is just the '03 without a USB port and less flash. It can't fit OpenWRT.
Edit: Ahh. Looks like they superseded it with the TL-MR3020. The bad news is, it costs $33. The good news is that it has a software readable 3 position switch on the side that does seem supported under OpenWRT.
Be careful with model or even revision numbers, always check hardware compatibility lists. very often times the difference between something like a "653" and a "653+" can be an entirely different (and not supported) chipset.
http://www.tp-link.com/en/products/details/?categoryid=&...
http://www.amazon.com/TP-LINK-TL-WR703N-Portable-802-11n-Wir...
http://www.amazon.com/TP-LINK-802-11n-802-11g-Wireless-TL-WR...