I still got some jon e fluid for mine, i bought a bunch in bulk very cheap and then worked at a spot where they didn't allow them (chemical plants) so i still got some left. From my understanding it's all the same product, naphtha, and are considered specialty naphtha blends because they are tweaked to certain uses such as lighter fluid, camp stove fuel, hand warmer fluid, thinner, etc). The best way to match them is to check the msds sheets and look at the boiling point of the "preferred naphtha" and compare it to the msds boiling point of the naphtha you want to use, i would bother with that only if i was gonna start using a new fluid in the handwarmers or a lighter since those are in your pocket.
Hardware and painting stores often have naphtha vm&p, which would work fine as a seafoam substitution too since it's just pure naphtha. I think it has a slightly lower boiling point, which would mean it's got more of the smaller c-h molecules, which means it evaporates quicker so it makes one of the best oil paint thinners out there, which is exactly how seafoam works. I just looked for it at menards online locally, it's 16 a gallon. All it does is dissolve the heavier hydrocarbons that have been left by replacing the old ones that evaporated out, which allows it to clean and restore the gas enough to run better. The diesel (or better yet kerosene) acts as a rust preventive and lubricant, and the ipa (heet is a common brand) dissipates the water by forcing it to mix in the fuel so it will stop separating out. I start with the naphtha, if that doesn't get it i as heet, and if I'm not lazy I'll give it a shot of kerosene since the heet was needed to dry the gas. I'm sure seafoam is better, but naphtha is cheaper so it suits me fine for when i let something go too long without running it a bunch. On a saw or other small 2 stroke i would simply dump it out and run the store-bought premix gas since that'll fix it too, and that's all i run anymore anyways.