Maybe try looking at UHMW (HDPE) linear guides, which certainly have the duty cycle you need, or possibly go the other way and consider turned polished steel "mushroom" pegs running in a track machined from 40 to 50mm thick UHMW plastic (HDPE 1000 grade).
What about something like small skateboard wheels running in routed out tracks in sheets of MDF/PLY? You could even double up the thickness of wood to add depth to the tracks.
Having looked at the price of UHMW sheet I think that route is not feasible, as it would seem to increase the budget of the entire project by about 200%. However, I think that the general idea is sound, and that guides made of ~25mm ply, with UHMW friction surfaces would work well. Thanks.