To save $$ I decided to build my own timing pulley's using the Grizzly mini mill and dividing head. I used the same
    pitch as the timing pulley that is used on the 9 x 20's ( XL ) which is a 1/5 pitch. The large timing pulley shown
    above is 82 tooth and a little over 5" OD. The smaller timing pulley shown below has 18 teeth and is the same as the
    smaller gear used on the 9x's.  If you don't have a mill and dividing head or rotary table with indexing plates the
    following info isn't going to help much. There are a lot of companies WM Berg , WW Grainger , Motion Industries
    who carry timing pulley's & belts but they can get expensive. Or another option might be to use regular V belt pulley's.
        Another factor to consider will be the DC motor's rpm's , the DC motor I used is rated at 4800 rpm. All the work
    I do with my 9 x 20 lathe is at the slower speeds ( 400 to 600 rpm range )  I have never used 1000 +. Because of this
    I used as large of a pulley as possible for the largest pulley that would still let the hinged cover to still be used. It works
    out that using the 18 tooth and 82 tooth gears I have a ratio of 4.56 to 1. With the 4800 rpm motor this means I will have
    a maximum rpm of approx 1000 rpm at the spindle. The lower gearing also provides more torque at lower speeds for
    threading.
   To determine the belt length need just use a flexible (cloth) tape measure such as found in sewing kits.
   Wrap around the pulleys and see how many inches you have. Add a zero to this and you have it.
  Example:  a measurement of 17" would be a 170 XL belt.   My setup had a measurement of  28" or a 280 XL belt.
  Some companies  such as Gates don't show the longer belts but a lot do so check around.
  I purchased two 280 XL belts for less than $ 20.