I had one made at an upholstery shop out of marine vinyl over heavy foam. I think it was $85. It's held up well. Any decent car upholstery shop could do it.
Picture a right angle triangle (a2+b2=c2).
The a2 part is fixed at 14.5" and the shaft plane c2 is 20". b2 is adjustable for different lie angles.
Martin,
What length do you use (Plane Line length) and what lie angle you find most beneficial? I use PVC which adapts for all club lie angles, but is to cumbersome to transport.