The Raven Guard Chapter Transfers are sold out. I got a reply from GW US Customer Service today confirming it.
It seems utterly ridiculous that these are limited stock only items. While I can see some chapters having only a very small market others are going to be much larger. Hopefully we'll see something like Black Library's print on demand in the future to serve customer needs. I suspect we'll see more of these release though, probably followed by some coming back into rotation.