Buy 3 of these "Swivel Caster - Gray Soft Rubber Wheel" - Model 3 = $30
Two pieces of whatever wood = $??
A few screws = $0.??
1. Screw 2 pieces of wood (42" and 36", but the length is very flexible indeed) together perpendicularly.
2. Drill holes at the end of the piece of wood and mount casters.
3. Put a screw through the piece of wood above the wheels as shown if you want some wheel angle control.
4. Put your tripod on it. Secure it with cable tie. Done!
It can travel in a straight line or in a curve, somewhat.
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