I've used theater gels to make computer screens "safe" to use with night adapted vision in observatories. Rosco and Lee are the two big names in the US, and you could find them online from a theater supply house or at a local theater or studio lighting supplier. Lee doesn't have a great online set of information to choose with, but Rosco has transmission charts at:
http://www.rosco.com/us/filters/roscolux.asp#SPECIFICATIONS
Look for the amber or red filters that stay away from the wavelengths where your materials are sensitive. You should be able to find a sheet about 21" by 24" (but double check me on size) for well under $10 plus shipping.
Wonder if there's a "development by inspection" green...
Lee
I just checked, and it appears that B&H and Calumet both carry a good selection of the Roscolux filters in stock. These should be tougher than rubylith, and the #27 should do for red light. Sheets are 20"x24", and you can double them if needed. There's also an amber that might work, depending on your paper, and a green diffusion material to try for development by inspection.