DR marine sells a replacement (see link below). They may even have a dimensional print that they could send you. They've been very helpful in my dealings with them. I know I've found another website that sells replacements but haven't been able to track it down.
I have a stern rail on my p26 but it was damaged at some point in it's history and was repaired with welded stainless tube sections and rebed, the result being is it is not symmetrical so the dimensions may not be very useful. I'm looking to replace it after next season so if you do find something, please let us know.
DR Marine Product List