Omicron obtainment query

I've been looking into some GAC Omicrons I could get with my current Toons to potentially boost my chances of success in GAC (rather than relying on players who don't even turn up), but I'd like to know any sources of obtaining Omicron materials other than purchasing with real-life money. I am getting one Mat per GC (none if I'm unlucky), but I do know that 3 Cantina Nodes that have them yield an exceptionally low drop rate. Where else can I get Omicron Mats?