Which part of MI will you be in? In western part of the state, along 31 from state line up to Muskegon, I usually find beans at CVS. YMMV with Wesco and Speedway stations. There's a Holiday station in TC that has them, but cc use requires manager override. SuperAmerica station along 94 has them (I think its near Stevensville), but also very spotty on accepting CC. Always looking for friends, but outside of GR, not a whole lot of competing players, so no problem in disclosing. I've not hunted in Detroit/Ann Arbor area for over a year, so can't help you there.