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I forgot about that, now I'm have second thoughts on 45. there's a dealer here who has a good selection of sigs but haven't stopped by yet.Part of the issue with the 45acp availability is that the FCU is different....it's not swappable with the 9/40/357 model. add to that the high demand, so they're tough to find. i would track one down via gunbroker or Sig. that is your best bet. unfortunately unlikely to find one at local dealers.
in terms of safety vs no safety, i do not understand why one would want a thumb safety but this is personal preference so I respect it. however I'm not sure Sig has produced a P320 45acp model with thumb safety. if that's your preference I would call Sig and ask them, since it might not even exist.
on the new P320s is what style of slide lock you have. It looks like they have a newer slide lock style out now thats becoming "Standard" its much lower profile