Places to buy Stabilizer
I bought wide stabilizer at Ken's Sewing Center. It is an internet business I use a lot for both Janome accessories and a lot of other stuff like thread and stablizers. They have they're own brand which I have found just fine, and they sell other brands too.
I also have bought both stabilizer and thread from a site called Sew For Less.
Usually Ken's delivery is very quick while Sew for Less sometimes is slightly slower although both have been really good.
Even the 5x5 hoop seems to take pretty wide stabilizer because of the design of it, which kind of irks me.