Chastity and orgasm denial discussion

Okay…To start with, I hope I don’t come across as foolish. I’m just getting started in the chastity lifestyle. I’ve been browsing for that ideal device suitable for constant wear—24/7/365—but it looks like securing a truly stable unit will cost me several hundred dollars. The issue is that since I’m spending this much, I need to be certain my measurements are spot on. Yet, every website seems to offer slightly different guidelines for measuring. I’m in search of reliable measurement methods or perhaps someone experienced who can handle the measuring process for me. I reside in San Francisco. Any assistance would be appreciated.