I'm not close to SF Valley, so can't help you with that. But most LFS have pods available.
I think the Tisbe pods will easily grow and reproduce in any system. Even in your main display since there is lots of hiding places under rocks. I also just use a clear container, add some phyto or every small flakes, and tank water....and add some Tisbe pods, and they grow well.
I'm also thinking about growing some Tigger pods, and using some of that reef nutrition tigger pods. But have not gotten the okay from the wife to have a container of green water outside to grow the pods.
Congrats on your mandarin. Hope yours will eat other foods too. My mandarin actually eat flakes, but I still add a lot of pods. He is fat and happy.