I was able to locate one by calling a local high end camera store that had one in stock with a RF 1.4 TC as well and was able to order it. The store was about 20 mi from me in Berkeley, CA, and that’s how I knew about the store because it had used it on occasion in the past. Unfortunately when I ordered it, I was on the East Coast and had to have the ship it to me there, which added to the expense but it was great to be able to get it. I had called every big known bulk camera store all over the country before that, and no luck. Maybe try to find a list of smaller more specialty, non chain camera stores (very rare) but that might be where you can find one–at least, that’s where I lucked out back in March.