The kind I preferred is the straight C-41, it has no suffix. (e.g. not RA, LORR or SM).
Basically I would shop around to see who has it the cheapest, with shipping. some charge hazmat for shipping which ups the final cost. Adorama, B&H, minilab supply, Pakor, are all places I have used or would use. There's others too of course, Unique is certainly a valid vendor.