IF truly NIB, 550 USD
Both. .45 Auto and .45 ACP are the same round.
THE GALCO S.O.B. AND THE FOBUS LEATHER PANCAKE MADE FOR THE GLOCK MODEL 21 WILL ALSO FIT THE 21SF
In what condition? Used and abused? $300-$375. Depending on your area. New? $500+. Again depending on your area. Typically $400-$500
a good custom leather holster is great but BlackHawk! serpa line may have one.
This website has what you need for you question. http://www.blackhawk.com/product/Sportster-SERPA-Holster,1146,1410.htm
SF = "Short Frame" The short frame was originally designed to compete in the U.S. military Joint Combat Pistol trials for a new .45 ACP pistol to replace the M9 pistol. This was achieved by a reduction in trigger reach and a reduction in heel depth.