Hello,
Options, options, options...there are so many for you to choose.
1- Find a trans friendly doctor and bring them a letter from your therapist stating that you know the consequences of hrt and you are prepared for the effects. Also, being a copy of WPATH 7, an informed consent form for hrt, and a reliable source on hrt dosages for trans guys. Being prepared is very important as it A) ensures that you won't have to come back again because you didn't have the info/documents, B) makes you look mature and responsible, and C) makes the doctor more comfortable in prescribing hrt.
Always keep in mind there are always exceptions to rules...since rules can be broken.
Or
2- Go to an endocrinologist (possibly with a referral from a GP). And of course, be prepared as in #1.
-Skye