I’m going to disagree a little with what webber said about casino groups having a third party network manage their affiliate program. While this might be true for a couple, the majority have inhouse affiliate programs as far as I’m aware. Thinking of the top 5-10 programs, they all have inhouse affiliate programs and do not rely on a network to manage their affiliate program.
In saying this though, some groups will choose to also work with a network even though they have an inhouse aff program.
Gambling affiliation rings a bell, as does income access. Obviously these are not as big as something like commission junction (which also has casino groups btw including 888), but they are probably your first bet. I can’t think of any other casino specific networks from the top of my head.
Good luck.