I got mine on peppermint.com, but that was five years ago. I don't thing they have them anymore (or maybe it's just an out of stock issue?).
Could you make one?
Not to make your craving worse, but I LOVED the Onbuhimo and used it almost constantly. It really was different from my Mei tie (I don't know how to spell it either!) because there is only ONE tying point, and I prefer the way the weight is distributed. I'm small chested and have difficulty tying mt the way I tied the Onbu (above my chest, w/ ds in a high back carry so he could see well over my shoulder.)