You can phone Computer / Network installing companies that you can find locally. - Not all of them are overpriced, but you would have to find the right one.
Doing I.T. things we use them daily since rack equipment is hardly standard when it comes to the depth that things are mounted. Generally in a full length server cabinet it's not strange to have 3 different depths to deal with.
Not sure about cape town, but up in JHB you can speak to Industrial Rackmount Solutions (
http://www.irsolutions.co.za/).
Otherwise as others have mentioned you can get usually get an engineering company to make them for you, which is what I did for a custom cabinet.
