I don't think 2260 was ever that common. It's probably not worth the hassle of finding one and sourcing it.
https://www.amazon.ca/dp/B00KLTPT6A
That's the only one I can find, and even then, it's not really a good deal at $154 for 256GB.
I bought a Crucial MX300 512GB M.2 2280 for $180 like half a year ago (albeit NAND prices have went up since) and it's now $197.