My past experience with my builders getting weather resisting sliding entry doors on catamarans has been bleak.
They were fantastically heavy, and expensive.
I had always thought some tiny Harken cars and tracks would be a good way to go. The sliders could be composite with Acrylic, or just Acrylic. I never had the time to track it down though.

One of my sailors, Peter, sent me this link. This could be the deal. A door truck shown below.   They have a lot of other boat things I see.

http://www.boatoutfitters.com/boat-sliding-door-hardware.html