From the looks I would guess at some scintillator (with a photomultiplier for readout, see here for first details: https://en.wikipedia.org/wiki/Scintillator)
These are usually custom made (and/or can be assembled/changed/... easily) so that the exact shape is not necessarily commercially available in bulk, but this should not matter for such an application. I would estimate 1-1.5k $ for the scintillator + PMT + the necessary High Voltage supply (another couple hundred bucks). PMT typically output small pulses (on the order 100mV) which you have to detect a flash ADC or similar will easily cost the same once more.. and then you still lack the Macbook;-) so nothing for the weekend project.
Slashdot Mirror
From the looks I would guess at some scintillator (with a photomultiplier for readout, see here for first details: https://en.wikipedia.org/wiki/Scintillator) These are usually custom made (and/or can be assembled/changed/... easily) so that the exact shape is not necessarily commercially available in bulk, but this should not matter for such an application. I would estimate 1-1.5k $ for the scintillator + PMT + the necessary High Voltage supply (another couple hundred bucks). PMT typically output small pulses (on the order 100mV) which you have to detect a flash ADC or similar will easily cost the same once more.. and then you still lack the Macbook ;-) so nothing for the weekend project.