This project is actually a few years old, I'm just now posting it because I didn't have a account back then. The first thing I did to the Geiger counter once I got it was power it up on a mains Variac (an variable transformer in for those who didn't know), (full bridge rectified of course) to replicate 90v DC without batteries, so I could test it. There was a possibility that the Geiger-Muller tube, even though collapsed, would still work. It didn't. And I had the Uranium glass to prove it. So I set out to find a replacement. As expected, finding a particular 60+ year old electronic component as obscure as this isn't exactly the most practical or economical thing in the world. Examples of Victoreen 1B85 GM tubes are few and far between. And when you can find one, they're expensive and similarly collapsed. Research revealed that Victoreen replaced this tube with a redesigned and reinforced version after getting reports of how easy it was to collapse, it's an air-tight tube with low pressure gas inside, made up of thin sheet metal. A cold day would do it in. So I began looking for substitutes, A suitable one came in the form of an eBay soviet surplus SBM-20 GM tube. The main reason I chose this tube is that the specifications were similar enough that I didn't need to modify the circuit to use it, but I did make some wood inserts so I could interface the SBM-20 to the mounts for the much larger 1B85. After this was accomplished it was back to the bench for some testing on my variac. It worked just fine. Now to solve the battery problem since I can't exactly carry my variac around to use the Geiger counter. After a long search I found an industrial supply company (I don't recall the name) that still sold 45v B batteries. I could have bought from them, but the batteries were like $50 each and I needed two of them, not a price anyone wants to pay for something as temporal as a battery. Because it is the 21st century, however, I had other options. If one goes on eBay looking for buck-converters, (which are basically switch mode power supplies that employ coils and capacitors to produce a higher voltage output than the input), they will find lots of cheap options. "Bingo!" I said triumphantly. I bought six 3v input 15v output modules. The plan was to wire them in series and get the requisite 90v output. The reality was a little more disappointing, the modules just got warm and nothing happened. So instead I opted for a different, much larger, single buck-converter that was designed to step up 12v to 60-90v (I think). I powered this with eight AA's ( 1.5 * 8 = 12 ) and the whole mess fit snuggly in the original battery compartment. To finish it off I hot-glued the buck-converter to the underside of the battery box and used some leftover anti-static foam crammed between original D batteries and the AA battery holder to keep it from rattling around while still being easily removable. After some tinkering, this Geiger counter is just as good for preliminary radiation detection as any of it's modern counterparts; and much cooler in my opinion.