There was a thread on MLU a little more than 2 years back where Dennis Walker had a bunch of pieces for sale on Kijiji. Thread is here:
http://www.mapleleafup.net/forums/sh...ht=searchlight
In a photo of the 25 pr chassis he was selling, I noticed a bent piece of metal in the background and recognized what it was. Another photo of a CMP trailer chassis had the base. I called Dennis, made a deal for the 25 pdr chassis and also a deal on the twin 50 mount. I went out in the spring and picked up both. To my pleasant surprise, Dennis had pretty much all of the small bits and pieces for the twin mount, and had already restored the sight assembly.
Here are the original photos from the ads, copied from the other link.