[Laser] cheap filters

[Andrew T. Flowers, K0SM]

Anyone have any suggestions on cheap bandpass filters for visible red 
lasers?  I'm looking for something that would pass 630-700nm, but have 
substantial attenuation at 850nm.  The reason for this is to get rid of 
the 850nm line spectrum from sodium lamps.  I'm thinking about 
cellophane or plexiglass that I might be able to find easily.  I thought 
I would ask here before I went to the lab via the craft store....

Andy