Imperial exited the market in 2013 and Heirloom has exhausted its supplies of spare parts. Heirloom has identified for most products an alternative button/valve combination.
Alternative parts are available but both the button AND outlet valve must be replaced
Heirloom does not supply Fluidmaster products but they are available from leading plumbing outlets
In all cases the Fluidmaster 560AU02 outlet valve will replace the Imperial outlet valve
The Fluidmaster button to partner with the valve are as follows:
Imperial Round Dimple button: Fluidmaster 560AU38 (Diameter 38mm) Button
Imperial Round Button: Fluidmaster 560AU48 (Diameter 48mm) Button
Imperial Oval button: Fluidmaster 560AU72 Button