Cheap source of linear polarised 45/135 glasses?

[syllopsium]

I've a Redrover SDM-240 passive 3D monitor arriving soon - it uses two monitors with a mirror and needs linear polarised 45/135 glasses. I can find one source of these in the UK, but it's not exactly cheap, and I'd like to prove everything works before buying a high end pair of glasses.

Is there a pair of glasses, off ebay or similar, perhaps one of the identifiable older IMAX ones (I know some were 45/135) that can be used without dropping fifty quid on a pair? Yes, I can find lots of glasses but most are circular polarised, and most of the IMAX ones will be too as the technology has changed.

[syllopsium]

IMAX can be any of circular polarisation (most recent), 45/135, or 0/90 depending on the technology. It seems difficult/impossible to tell the difference, which is why I'm asking if anyone can reliably identify suitable ones.