Are the Harpacticoida surface dwelling? Apparently they are in the pods that I was dosingHaha, your question is a good one and is the exact reason you see tiger pods as being the most available.
Tiger pods are the most widely sold because they can tolerate the widest temperature ranges, and for the longest times. Hence, they are the easiest to sell and hold in inventory.
That said, there are tons of sites that sell apex and tisbe pods, including reef nutrition. I’ve had lots of success with both so if you just want to order a bottle of apex from the reef nutrition website, go for it.