You might try
http://www.grindergear.com/
or you could get a sports-CD case like the ones at
http://www.casedirect.com/cgi-bin/sg...dplayer-active
some of which will comfortably fit a PDA.
Or you could just do what I do, get a cheap fanny pack and add some cushioning in front of the Axim Screen. A bit of foam or a dry plastic sponge wrapped in a microfiber cloth works very nicely.
If you're sweating up a storm then a plastic sandwich bag around the Axim with a twist tie fastening it around the earphone cord works well and you can take the Axim out and press buttons without opening the bag. The fanny pack also has another pocket to hold keys and wallet. It's inexpensive, light, and I think it works better but this is not the stylish approach.