I teach UX designers across North America how to apply behavioral psychology to tech, so I can share a bigger-picture perspective on your question.
My most serious students completed their Masters or PhD in HCI, especially those on the west coast of America. And a few others got their post-grad credentials through an interdisciplinary program by combining UX with another topic.
UX is a generic skill, so if you want to specialize in a niche UX application, you’ll either have to to find a formal HCI/UX program that has a flexible thesis option, or target some other faculty and pitch your UX thesis to the faculty.
I taught a course of UX Masters students in the iSchool at the University of Toronto last year, and I was quite impressed by their program. Their UX stream is grounded in formal HCI and interaction design curriculum. But what’s amazing for students is a large number of electives and great options for research, so you can probably fine-tune your Masters to get exactly what you want out of it. It’s also a wonderful place to do a PhD if you want to go further. https://ischool.utoronto.ca/