Tripod bowl adapter?

Anybody know where or what I can do to inexpensively step down from a 150mm bowl to a 100mm one? Sachtler wants $235 for the step down ring and that seems like a LOT for something so simple.

Thanks, Scott. But the problem I have would need a REALLY good kludge as I'm using big Sachtler sticks with a 150mm bowl to support a Jib arm with a 100mm base. The weight of the jib pulls itself out of level too easily. When I use the bottom nut from the 150mm head it holds for a few hours so for now maybe that's the best I can do.

I also hate renting because of the hassle of picking up and dropping off or the expense of having stuff shipped to many of the smaller markets where most of my work is. And frankly I'd rather spring for a 100mm heavy duty tripod than spend $235 on a ring of metal. At least that way I'd feel like less of a sucker.