I graduated in 2015 with my Bachelor's neuroscience. I've been doing social science research for think tanks since then, and I'd like to make a transition into a sociology PhD program. I have a good GPA (3.9) and GREs (166V, 167Q) and lots of sociological research experience. However, I don't have any letters of recommendation from sociologists (I work mostly with psychologists and economists) and didn't take any sociology courses in undergrad.
I'm wondering if there are any full-time jobs I could work at (or maybe a Master's, but those are expensive) that would improve my chances of getting into a top-tier sociology PhD program for entry in Fall 2020 or Fall 2021. I know there are a lot of Research Assistant, Lab Manager, and even Predoctoral Fellow positions in psychology, economics, and other disciplines. But I haven't been able to find many for sociology per se.
Any ideas?