I belive that Royal Crown and 7 Up are one in the same.
Because not many places carry 7 up products on fountain due to Pepsi and Coke that might be why it is hard to find RC.
Best bet is to look for not only RC but any 7 up product on fountain. Once you find a place ask the manager who the local distributor is for the syrup. Once you've got the local sales reps number you can call and ask where the nearset RC fountain is (he'll know his route by hart and it will probably cover a wide area near you). If your really desperate he can run a contract with you to carry a 7 up soda fountain (they usually lease the equipment on a contract basis for a certain time period as long as the equiptment only dispenses 7 up products). The distributor can sell you the 5 Gal BNB syrup (bag in a box) which will probably run you about $50. (BTW they rig the BNB connection to be proprietary by brand - i.e. a Coke BNB will not connect to Pepsi fountain equiptment. There are ways around this though) The soda mixes typically at 5 to 1 (5 parts soda water to 1 part syrup). This will yeild 30 Gallons before you will have to change the BNB. How much can you drink in a month? LOL
Oh, I for got to mention....places like 7 11 or Circle K make frachise nationwide deals which allow different brands to exist on the same soda fountain equiptment. These place usually do not deal with a distributor (or at least they don't have to) because they can get all the syrup they need from their grocery distributor.