kensuguro

I've been out of school for a while (10 years) and applying to grad school. (mpp) Problem is, some schools require 1 LOR from an academic source. What's considered an academic source? Of course, a professor who you directly studied under is probably the easiest, but as I'm in a different country, and especially since I've been out of school for so long, it's not a realistic option for me. I'm wondering if just any professor is okay? I know some professors I've worked with, but not studied with.. so I know them in a professional capacity, but they themselves are an academic source.. Are phds good for this too? I know some hard core researchers.. My question is, how does one go about finding an academic resource? Is the only choice to back track to undergrad and hunt down my professor who doesn't remember me?