I was searching for the same thing for my T|X (direct connect keyboard), but it doesn't appear that such a thing exists. I was very hesitant to go for an IR keyboard, because I felt for sure that it would use more battery life and the batteries in the keyboard would die quickly, etc. However, since there wasn't any other option I ended up with a Palm Wireless Keyboard (older model, 4 rows) from eBay for $20 new.
I really like this keyboard. It doesn't have the problems that the new Palm Universal Wireless Keyboard has with regard to drivers and the T|X, and it's not too much bigger than the T|X in a hard case. I don't know about the new Palm UWK, but this older model is actually a Think Outside product, and you can use their latest drivers on the T|X without a hitch. I actually went back a couple of driver versions because I didn't like the way the latest driver has Bluetooth support in it. I was worried that it might activate my Bluetooth from time to tome, causing more battery drain. The driver I'm currently using only supports the direct connect and IR keyboards by Think Outside.
At first look, it appears to be impossible to use this keyboard with the T|X in landscape mode (without switching it to left-handed landscape mode), but if you rotate the IR wand all the way over the right, it works just fine with the T|X in normal landscape mode.
You can get the really good deals on the Palm Wireless Keyboard on eBay since the newer model is out. I don't really see a reason to pay more for the newer model, but some people might like having 5 rows of keys instead of 4. I adapt well to keyboards, so the 4 rows doesn't bother me.