I have a VX nano but still felt it was a bit bulky for travel. During holiday clearance at Container Store I found this Xoopar Pokket for $7.50:

http://www.xoopardesign.com/product/...=5&xooparboy=0

It's very flat and fits into a slim business card pocket, yet has a great scroll gear on the right side I can turn with my middle finger. The construction is sturdy and the buttons have good tactile clicking. Also the cord is removable so you can use the same mini-usb cable you use for mobile charging for the mouse - one less cable to carry on the road.

It's not in many stores, but you can find it on eBay for about $20 shipped.