WCU,
I have some nice plexiglass display covers approx 4-5" wide by approx 15" long (I say approx as they are not immeadiately accessible to measure). They are brand new in individual cardboard boxes.
They do NOT have wood bases, but you could improvise there, or just set it on the track on your wood desk top.

O scale car inside,..

Two HO engines side by side,..

very reasonable,...send me a private email message (NOT forum private message) ...... railandsail (at) gmail