I have a splined adapter that I sleeved and bored to slide over the "spindle" of most balancing machines (1.574 ID). I also bored the center of a knock off out to the same ID. Simulates the same geometry of your car.
I'll gladly lend the set-up to you if you'll pay postage both ways. Fits in a USPS flat rate box... $12.35
If you're interested, verify the OD of your balancer.
Paul - are you trying to get the wheels balanced while they're on the car?
When I worked at the import shop I used to balance a lot of wire wheels with a bubble balancer.
Thanks Walter, That puts a new light on bubble balancers. I just wish we were close to North Carolina, as Hendrix did the wheels on our 72 B and the difference was amazing. He trues the wheels, tunes the spokes and shaves the tires for out of round, not cheap but well worth the price. PJ