Most every overseas base has a military notary assigned somewhere? Army, I'd imagine at BN or BDE S1? Air Force, there is usually one in the Force Support Squadron. Don't know about Navy/USMC.
I had several documents notarized by military notary while working as a contractor in Oman and UAE. Understand things may be very different in Poland if your location was only recently "stood up"? Then again, I may have totally misunderstood your situation and what you're trying to do, lol.