Hormone blockers for Estrogen are few. They aim to stop, or grossly reduce, the production of Estrogen in the ovaries.
Now, I did get a blocker just prior to starting Testosterone myself.
I got an implant which is typically given as a part of hormone-related-cancer-medication (breast cancer, prostate cancer, etcetera) and it works by overloading the system in charge of regulating hormone production in the ovaries and testes.
This meant that I didn't have to wait for Testosterone to work it's magic and shut down the reproductive parts and so I haven't had a period since I got that implant and it only lasted three months (and it's been over a year since I started Testosterone).
I can not remember the name of the implant I got but I do remember the price.
Due to it being classified as a cancer medication it was fully covered by the Icelandic single payer system, but I did get a receipt for it none the less. I had to pay 0 out of eighty thousand Icelandic krónur (680 american dollars, 425 british pounds, 507 euro).
It may be at least a part of the reason why most trans-men don't get blockers, or at least not this one.
It is not cheap!