1. UTFSE
2. Industrial Supply Stores ussually sell both 5, and 55gal containers
3. Commercial paint supply stores ussually stock 5gal, and if big enough 55gal sizes
4. Most city dumps have a solvent reclaimation program and will be more then happy to give you whatever you need for free.
5. Get the DOT#'s off rhodium's site and make a trip to the local train yard with some 5 gallon pails -- never know what you might find.
6. Got to a hardware store designed for contrators mainly, and ask about 5gal sizes of solvents
7. Solvents are ussually less exensive then you think when bought by the drum.
8. That should get you started
DOT# link:
https://www.thevespiary.org/rhodium/Rhodium/chemistry/popeye/popeye.dot.chem-id.txt