I have a master's degree in theoretical physics. I want to do a PhD and start a career in research.
The problem is my letters of recommendation. I had a horrible relationship with my master's supervisor, who was also my undergraduate supervisor. I ended up graduating, but with no publications and no thesis. He will not provide a letter. I've already asked other professors: some said no; a few did agree, but they don't really know me. My field is very theoretical, so getting a job and asking my boss for a letter does not seem like it would be helpful.
The only thing I can think of is to do a second master's degree with the specific goal of forming relationships with professors who can write me letters of recommendation. Does this seem like a reasonable thing to do? I'm scared about getting too old or failing again at the thesis.