In the Houston area you are bound to have bearing and precision parts suppliers listed in the yellow pages. They could look at the current rack and measure it for match and order a piece for you. One such company in Omaha that is nationwide is Precision Bearing and Manufacturing. Example for cost would be a 12" length 32 pitch 3/16" brass rack is $22.38. The gear rack now on the camera may be carbon steel, and they are less expensive, but a brass gear does not rust and is easy to drill and cut to size if you do it yourself.
Measure the teeth in an inch and the width of the rack. How long a piece would you need and what is the camera model? I have a variety of pieces around here in both brass and steel. Maybe something that will work. you can have it for a lot less then the above price.