100mm non-L Macro collar question

I just purchased a used Canon tripod collar (the B type) for my 100mm Macro non-L lens from B&H. After trying to fit it for an hour, I finally googled it and found that they come with a plastic adaptor ring to mount on the 100mm, and the ad stated that it fits that lens. Didn't say that the adaptor was missing. B&H is a great store, I'm not holding any grudges about this, these things happen, but I'm so disappointed.

Before I return it, does anyone know if and where I can purchase the adaptor? I've looked for a Canon parts catalogue online but got nowhere. I doubt B&H stocks them (they're closed at the moment so I have to wait until tomorrow to call).

I'm in Canada, by the way. And thanks for any tips.

Cheers.

The adaptor comes with the TMA AFAIK, else you have to order it. See my web page notes on this.

Note that, it works but is not as smooth as with other lenses that don't need the adaptor, you have to slacken off the lock knob a lot more to get free movement.

Very interesting site Lester: many thanks!