The battle is Sangshak India. I have descriptions of the area but not many measurements
If your map is handdrawn, it will most likely be only a rough map to begin with.
Sometimes, aerial reconaissance photographs of WW2 are available for military important areas. This is the case for most of Germany for example.
For small settlements in the far east jungle, this might be less likely, but it could be a starting point for research.
Assuming, such photo footage exists, then you could - maybe - compare the layout of huts on your plan with that of the aerial photograph.
If you find a possible match, then you might be able to pinpoint the exact geographic location in the next step.
After that, you could draw on modern maps / google earth for more specific terrain info.
Probably, this will not work - but at least, it is a plan to approach the issue.
In case you can only roughly pinpoint the location, then modern maps / google earth will likely still be able to give you a general impression of the terrain. For anything but a detailed HASL, this should be sufficient, as any geo-board is abstracted landscape in the first place. So for geo-board designs, it is more important to get 'the feeling' right rather than finding a very similar map layout, which would likely not be available anyway.