I don't know the status of availability of rebuild kits, but I ordered some replacement complete cylinders from Mico in 2008 through a local distributor. The part number was 03-20-455. At the time, wholesale was about $300. each.
I attempted to order additional units in June of 2022 but the supplier informed me that the replacement is now obsolete and they could find none in stock anywhere.
I attached some photos of the 2008 replacement so in the event you find anyone claiming to have one, you can use these for comparison.