Go on Ebay and the WW2 militaria section. Once there, type in rangefinder.
They aren'talways on there but do show up occaisionaly.
At this point in time, id suggest a Wild, due to the age factor on most others, although ive seen post war Barr & Strouds also.
Also, one never knows for sure how long they will last. We still have a WW1 unit in use by a camp member and its still in fine shape.
Expect to pay three to five hundred for one in good condition, not to say you wont encounter ones at higher prices.
Check with Deitsch optic in California, as they have had them from time to time also.
They had lots of new never issued Wilds for as I recall $300 about 10 years ago.