DRO on a 12X36 lathe

I am looking for a digital readout preferably with rpm as well that uses "
glass scales" there must be a few out there. I am not interested in the
full CNC just the measurement aspect. this will be going on my first lathe
and the lathe is a new thing for me. I am a electronic tecnecian by trade
and have been working wood for a number of years and have recently gotten
interested in turning metal. maybe a comercial DRO unit, but where to
start. Expense is an issue so i am looking for used/refurbished equipment.
any help would be greatly appreciated.

Confused in WV.
archie =) =) =)