Have you tried making your own flax seed gel? It's not a leave-in... it's a gel/gellee, but you can add emollients to it (like shea butter or oils) to make it moisturizing. If you have issues with oils you may find a specific amount to add that gives you moisture w/out greasiness or weigh-down. Start w/ 1/2 tsp to one cup water + flax seeds and take it from there. There's a lot of recipes on this site.

I've used it on its own as a single styler and it helps w/ the moisture level and frizz.