I chelated using Amalgam Illness, the book available from noamalgam.com, and lived to talk about it.
Chelation ob the Cutler protocol is so inexpensive, it is not worth going into the trouble of getting a prescription, particularly since you won't get the ones you need anyway.
The only exception I can think of is if you need hormonal therapy for the adrenals and thyroid, but even then your chances of finding a practitioner who has the right ideas about chelation and puts your health ahead of their business interests (such as maintaining their medical license) are close to zero. Whatever you decide, get the book first. Your health - or whatever is left of it - is priceless.