IMHO, there's no really good reason to go with something other than a Ruger MK II/III or Browning Buckmark. None of the potmetal guns out there (SIG Mosquito, ISSC M22, Walther (really Umarex) P22, etc.) even come close in quality, durability, reliabilty, and shootability to the Ruger or Browning. Especially since some of those guns can cost as much or more.
S&W Model 41 is a great option too, but that's a LOT more money.