Can't answer your question but I'm starting my first Wabi-kusa in a flattened bowl-like peice of glassware I picked up at Michael's yesterday for 7 bucks. The ADA glass is no doubt superior but a lot more than I want to spend on an experiment.
What I'd like to know is how to do a knock-off of the soil they use which stays together without wrapping and tying it in Spag Moss. I was thinking about mixing some potter's red clay with enough water to make a slurry and then mixing the potting mix with it to hopefully stay together. Probably much easier to plant things in for grow out. Need to look into to this further.
That and what kind of cheaper LED fixture to light it up with. I'm all about saving money and DIY projects where it can be done ascetically.