If you live in the bay area, http://www.askergoworks.com/ is the only place I know of where you can actually try out various ergonomic keyboards,mice,chairs,etc. before you buy them. They have a showroom in Palo Alto where you can check out their products by appointment. One cool thing I discovered- they are a reseller for a custom office chair company- you can specify every piece of the chair to your liking: back, seat, fabric, hydraulics,etc.
I have no connection to askergoworks.com other than purchases I made there: both my kinesis keyboards+footpedal, and both my cirque touchpads.