Encoder and read out

Hi,

I have a table that is raised and lowered by a lead screw, a small DC
gear-motor and XL belt. I would like to add an encoder to get a read
out of numbers so I can position it without having to use a tape measure.

The read out does not have to be inches just numbers will be fine as I
can relate a count of say 1245 to 4" etc. When I need it at 4" I can
just run it to read a count of 1245. Inches would be nice but not
really needed.

Anyone know of a low cost kit that will do this?

Thanks in advance.

Dave