Steven, As much for my interest as yours, I have done some research on BAP output bearings.
According to Draganfly's BA gearbox listings, the same bearing, Ariel part number, 3095-31, was used from 1931-52. I could not elicit any size information from their web page.
casings the position of the mounting bosses of the sq4 gearbox shell is different to the other models in order to move the gearbox sprocket further to the left. part no. description per model years 3000-35u shel
draganfly.co.uk
So I measured a NOS bearing which I recently received. It appeared to be a straight forward 1 1/2 x 27/32" until I looked more carefully at the numbers. The OD measured 2.8346" But wait, 27/23 is 2.8438" 2.8346" = 72mm!
The bearing is Metrinch! 1.5 Inch x 72mm x 17mm which confirms folklore that Burman had their own bearing sizes made.
It is marked SKF W3500A
But 1.5 = 38.1mm. or conversely, 38mm = 1.496" Is it feasible to take .004" off the sleeve gear or hone 0.1mm out of the bearing, and use a 38 x 72 x 17 bearing? I went looking for 38x72x17 bearing on the interweb. I'm not convinced that they actually exist, there are web sites that will sell you anything you ask for, but that bearing size does not pop up as an ISO bearing that I could see.
I would suggest that the best you are going to be able to do is use this seal kit, available from Draganfly or make your own adaptor ring, and buy the 1.75 x 2.25 x .25" seal.
Good Luck