There are two simple answers if buying the entire sprue is not an option -
1 Since its just a visual adornment and not load bearing, why not just make one? A bit of styrene sheet cut to size.
2 Alternatively, just forget the wheels. Operationally, they are just a source of line snagging.
My second hand one came without them, and I have never missed them, a fellow club member has recently built one, fitted the wheels and has resorted to cutting bits off them to get a good run for his lines.