I've managed to put groups together for this many times. I will get as many friends/randoms to commit to helping me (or a friend) as I can, then find another group trying to find people, tell them which of the classes in my group need it, what we have available for them to use, and ask if they will let us join them.

It would be easier if hydra and chimera were next to each other without throwing a dungeon in between them though.