I'll be milling some moulds out of epoxy. I would love to try the s120 sealer but it's just too expensive to ship to the states. Does anyone know of something similar I can get here? Also I'm curious what type of epoxy/filler will work nicely for this? I will probably be building up a layer of epoxy over pre milled mdf leaving a few mm thickness for epoxy and milling final shape into that. Already tried bondo and that works, but I think epoxy/filler will work nicer and be tougher, just not sure what to use. Another guy mentioned coating the mould in Teflon tape which i might consider, but I want to see what is available to use that is similar to s120. 

Essentially yes. Not every company classifies their products like that which does make it a little tricky to find. The S120 is a new addition to Easy Composites lineup, but these types of products have actually been around for many years - Chemtrend have already phased out some of their older versions.

I did a hell of a lot of research to find an equivalent product that I could get locally, and in the end I found it by looking at the safety datasheets and comparing the substance concentrations.