bench top DRO

I'm looking for a cheap implementation for a 2 axis DRO on a benchtop
mill - about 30" by 15 travel. Looks like I can get some free
software to read encoders from Steve Lindsay
http://www.lindsayengraving.com/other_interests/dro.html
I'm wondering about buying linear scales and using them for the
encoders , I should be able to make them work, don't you think? And
anyone who has a source for linear scales or appropriate rotary
encoders who could point me would be greatly appreciated. Chuck