Go to the thread "Keyboards for the x50":
http://www.aximsite.com/boards/showthread.php?t=58868
For questions like this, you can usually find answers by searchin the forums (click "Search" in the middle of the menus at the top of the page - below the aximsite name and the ad). Try a search to get more threads.
You will probably have to go wireless one way or another, because I haven't heard of any other option for the x50.
I have the Think Outside IR, but I'm too scared to take it out of the box, thinking that the Palm Universal might be better. Ahh...decisions!!!