Undo that nut on the top, in the middle, the bottom and canister will drop out ...
Heres what a new one looks like ...
https://www.ebay.co.uk/itm/222520618352
Other sellers exist
An easy way to gain access is to release bonnet stay and lean bonnet back against screen, support with a long stick for safety.
As I remember the 19j filter is the old type that does not unscrew. A bolt on the top/middle part of housing goes...