Plastic scintillator from Eljen isn't very expensive, especially if you only need a few cubic inches.
You can do very well with optically isolated pixels stacked together, followed by a common diffuser, followed by a drift gap, then 4 pmts or a position sensitive pmt with 4 cathodes. This will let you identify the struck pixel with less instrumentation. You can passively couple the outputs with resistors to get a horizontal and vertical position signals so you only need 2 data acquisition channels.
> Plastic scintillator from Eljen isn't very expensive
Do they sell directly to private individuals? If not, where would I get some? There are some listings on eBay but not exactly the place I prefer to shop such stuff.
I order stuff from them all the time in small quantities to a university, and a normal person's credit card should be much more convenient for them than dealing with procurement beurocracy, net90, etc.
The plastic scintillator is chemically just plastic so there are no safety complications shipping or receiving it. You might have more trouble getting large amounts of liquid scintillator because of the solvents.
Another thing you might consider is scintillating fiber with wavelength shifter. If you read out from both ends you can estimate position within the fiber by timing and possibly amplitude weighting.
You can do very well with optically isolated pixels stacked together, followed by a common diffuser, followed by a drift gap, then 4 pmts or a position sensitive pmt with 4 cathodes. This will let you identify the struck pixel with less instrumentation. You can passively couple the outputs with resistors to get a horizontal and vertical position signals so you only need 2 data acquisition channels.