Note that the device will likely work just fine using a modern aluminum electrolytic capacitor as a replacement.
Tantalum capacitors were commonly used in vintage military gear for their small size and greater reliability than what was available at the time in terms of electrolytics. Nowadays, electrolytic capacitors have come down in size quite a bit and capacitors from reputable manufacturers are actually very reliable. Better yet, solid aluminum polymer capacitors offer even better performance and reliability.