look up in the old paper phone book, "propane, natural gas, heating oil", heating oil = diesel. colored red with a dye. and will stain any filters and like if used on a vehicle that drives on the regular road. with that said. call up local heating like companies that deliver heating oil, you may also see if there some wholesale suppliers for fuel.
contact local tractor dealer or another farmer near you.
there are business with this. a lot of industrial equipment, needs fuel, to large size ag tractors, to other. and companies just haul fuel around to were ever.
some companies have a pretty big area that they handle. as far as a service map, check various companies out on internet / give them a call. and if they don't they might have someone to get a hold of.
sorry not much help, with local doings, i normally fall to, the old phone and asking, generally get a lot of "nopes" but every now and then i get a phone number or a name of a person or a company, and i need to jot it down quickly. it kinda of a pain that way. but it has help me find some good folks and companies that way, for various stuff.