I built my own mount. I used 3" schedule 40 pipe that welds to the bracket. And used 1 1/2" schedule 80 pipe, for the slip ring to go in and this is welded to a bolt-on cap, that bolts up to a flange ring that is welded to a 4" schedule 40 pipe for the tower. The 3" pipe I split down the middle so I could fit the bearings into it. And I then welded the joint up. The inside of the bearing was a little bigger than the 1 1/2" pipe so I shimmed it to get a slip on fit. So the bracket with the 3" pipe and bearings slips over the 1 1/2" sch-80. It swings nice and smooth. It pays to work in a fab shop and get the parts burnt out on the plasma table. See pictures below.