Linear glass scales...dro

Does anybody have a source for "low cost" glass scales for DRO
purposes? Not sure yet if sinusoidal or Square wave quadrature TTL
signals are required for the counter I have. One time I saw some that
came from India, but can't find any info on anyone importing them.
Accurite,Hedenhain,Mitotoyo are not an option (too costly) and Fagor
scales are more reasonable, but still too rich for the project.

thanks
dk