Leon,
I did a very small run of these a while back and sold them to a couple of forum members. I wish I had more left and I would send you one, but I only have one left and that's destined for my bike. The cheapest, fastest way to get one is to just make one or have your local machine shop make one. It's ridiculously simple (if you bought one of my spacers subsitute "difficult" for "simple"). It's a tube: 114.31 mm X 25.10 (OD) X 20.50 (ID) or a wall thickness of 2.30 mm. A piece of 1" OD aluminum tube (use 6061 or 7075) will work just fine. Chamfer the inside edge so it's easier to put the axle through it.
If your local machine shop is unreasonable, then pop by your local university. The machine shop workers in either the physics or chemistry departments or the physical plant often do contract work.
Good luck,
Jason