There is no SAAMI Spec for "380+P" and as such no manufacturer will allow for it's use in their manual. What Sig does say in the P238 manual is this:
So that right there tells me that Sig is against using .380 ammunition carrying a +P designation.2. The use of reloaded, “remanufactured” hand-loaded, or other non-standard ammunition voids all warranties. Reloading is a science and improperly loaded ammunition can be extremely dangerous. Severe damage to the firearm and serious injury to the shooter or to others may result. Always use ammunition that complies with the industry performance standards established by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI) of the United States or ammunition manufactured to military specifications.
While some of the 9mm guns come close in size, the .380s are still smaller and some of the micro 9mm offerings don't have the best rep for reliability. So far I stick with the tiny .380s. A Kahr MK9 has been on my list for a while, but I can never find one to get my hands on locally.