I have this info from a good US source:
There is an issue getting cylinders at the moment both from Continental and Lycoming. Superior is currently outselling their monthly manufacturing capacity by a good margin. Of course there are cylinders that they do not have PMA authorization to make such as Lycoming angle head cylinders or the Continental cross flow heads (IO-550-N, TSIO-550-E). Continental steel barrel cylinders are easier to get than nickel, but it can be challenging.
And does anyone know why there is such a delay in obtaining Continental and Lycoming cylinders?
Extra demand, it seems from the above reply.
But if you use a good shop, they can probably still get them.
I looked up Superior cylinders for my wide deck O-320 at (US) Aircraft Spruce and find they have none, and per their website are expecting a shipment on December 7th.