Apart from the thin sections themselves, the polariser filters are the only component of the project that cannot be 3D printed (at least not yet in the visible spectrum of light!).
Thankfully linear polarisers are readily available online. It is absolutely key that you get linear polarising film. I have found that by searching for “LCD/LED Polarized Filter Polarizing Film Sheet for Polarization” on Amazon you can find decent deals. I have been able to find 30 x 20cm linear polariser sheets for about $20CAD for 5. with care, I can cut 6 filters for the slide viewer per sheet, bringing the price per filter to about $0.7CAD each.
Participants that will be hosting the traveling thin section collection will be provided with pre-cut polarisers to make things a little easier and reduce the financial burden of participation.