I'm not sure if you are looking for just full size pistols. If not here are a a few smaller examples-
North American Arms Guardian series. Small pocket pistol. Stainless Steel frame
Seecamp, small pocket pistol. The NAA Guardian is a later improved version of this.
Remington R51 and RM380 have aluminum frames.
The Bond Arms BullPup9 is double action only but it has a flapper/hammer and regular firing pin. The flapper only comes out when shooting it.