I have a good idea for an “upgrade” to the revolver depending on the timing of this new adventure. As long as its post 1935 the browning Hi-power is a good pistol that has nice magazine size, nice “damage”, and as an added bonus was indies backup gun in raiders of the lost ark.
The quotes around upgrade and damage are as a result of such terms being subjective in most senses. As technically the best gun you can use and is the one you can keep properly working the best. And damage is subjective as most bullets at the time around ww2 are fairly close in terms of combat effectiveness. (Most round types are still in use today)
The big selling point of the Hi-power compared to a revolver is the magazine capacity. Holding 13 or potentially more bullets, depending on variants, means more ability to defend yourself even if you miss.
Lastly if you wanted to name the type of revolver used I’d check out the weebly or the s&w 1917. Both were used in the indiana jones movies and actually indy’s guns have an entire wiki dedicated to them which might be a good starting point.