If you can't find plastic track, you might want to consider looking for extruded flexible plastic rectangular or square tubing and slit it down the middle to create your own tracks. If you need something with a deeper track, just cut the top off one side or cut to width.
When I was considering doing roll up windows on my car, I was going to bend some rectangular tube to the shape of the windows in the roller press (Harbor Freight $129) and then cut the top off the tube in my band saw to expose an open channel. There are a many options for rubber or felt lined channel molding that would be glued inside the channel. This would give you a very quite action and provide a little "give" to absorb shock etc.
Chris