Urological models don’t seem to be common (you can get bones, hearts, and a few other organs from the US NIH, though). However, one of the things I did turn up in a quick web search was several mentions of software that can be used to turn medical imaging data (MRI, possibly others) into models for printing. It’s usually used for setting up individualized treatment plans. Maybe what you need is a former patient who’s had the appropriate regions scanned and might be willing to release the data to you for such a purpose.