TargetTalk

Red Bluff made a side mount that mounted only on the left side is quite light and rigid. You may be able to find someone on one of the 1911 forums that has one for sale.

NRA rules 3.2, 3.3 and 3.4 say telescopic sights can be used on center fire pistol or revolver; .45 caliber semi-auto or revolver; .22 caliber pistol or revolver.

Ace Hardware; inexpensive metal type; short staples. Just don't leave it out in the sun on a hot day. Did that once while shooting the long line. Now I cover it with my clipboard.

You can always try the beer can shim (shooting and the zen of pistol maintenance).