Bausch and Lomb 800mm spotting scope

I have a used B&L 800mm spotting scope/mirrored lens, that is missing the camera extension tube mount that is required to mount a DSLR to the scope. It is a 36.4mm female thread to a male T-Thread. I understand from talking to B&H that it is probably a proprietary adaptor and I won't find an after market replacement. I'm looking for this part, or a used B&L 800mm scope part number is 61-8080 that has the part. Or I'm looking for another similar scope (used), any brand. I'm trying to compile parts to photograph the august solar eclipse, and the fact that this camera adaptor was missing from the set is a major snag. All thoughts and ideas appreciated.

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The adapter on the end is screwed to the mechanism and it sure looks like a typical camera T-adapter. The question is , which camera. They usually tell what camera on the adapter itself. What camera are you using?

Walt