I went to Cistus nursery (Portland) and, by serendipitous luck, met the owner. I explained to him that I was very interested in hardy citrus, had many rare obscure hybrids, and wanted to undertake a hybridization project.
I had seen C. ichangensis listed under the plant list on their website, but when I had called in, the person on the phone told me the only hardy citrus they had was Flying dragon and one or two citrumelos. I went there anyway, hoping to pick up a Green Gage plum (which I noticed was also on their plant list), and just to check out for myself in case there was a tiny chance the person on the phone was wrong (sometimes happens with nurseries).
The owner said he might have one or two ichangensis plants in the back, if he had two, I could have one. So I waited, and eventually asked one of the employees whether he could check on the situation. The nursery employee came back with a small C. ichangensis plant, and the owner was giving it to me free! (He said it was because the owner was expecting seeds from me in the future)
Unfortunately the nursery did not have Green Gage plum and I was told the nursery doesn't really carry fruits and edibles anymore. I did notice several Dicksonia antarctica tree ferns in the greenhouse, which the tags indicated could survive outside with some light protection some winters. And I also noticed a Flying Dragon growing outside in the bushes besides the entry road.
I do already have several cuttings of ichangensis but I was not entirely sure whether they would successfully root and survive (the tiny leaves looked like they took a turn for the worse after I removed the cling wrap that was covering the cups to hold in the humidity), so it's nice to have an actual potted plant that's established.