I forgot about Halloween stores >.<.
Just go in and ask what they have. Most of the stores near me don't sell the big litre bottles, they just sell small bottles and it goes by 'Fake Skin'. All it is is liquid latex in a small bottle, usually with a stippling sponge. It's gonna cost a lot more than buying a big bottle but it's a good last resort.
If they don't have it they may be able to direct you to somewhere that does, and some stores may even order it in for you if one of their suppliers stocks it.
If there are any stores near you that sell theatre-grade makeup, ask inside. Again, if they don't have it they could stock make-up by a brand that sells it and may be able to order some in for you.
Um, there's also one other type of store that would sell coloured liquid latex, but you really don't want to be getting it from there XD.