You'll be driving through Flint, which is my hometown.
There is a greek store in East Lansing that is called Spartan Corner. The address is 103 E. Grand River Avenue, East Lansing, MI 48823. Most of my sisters drive down to State to buy stuff since there isn't much Greek stuff in Flint.
Western Michigan University is in Kalamazoo so there is probably a store there as well.
I'll be on that side of the state on Saturday as well.