Override BackOffice View Handler

[Geronimo2012]

Hello,

In PS8.1 I'm trying to add a trackingurl that also contains a zipcode/postcode base on a template that includes a '@' for the trackingnumber and a '#' for the zipcode.
Some code I could override, for instance to correctly set the {followup} template variable for in_transit.

Now I'm trying to also display a URL containing the zipcode/postcode in the Admin Order Details View section carriers.
I can change the handler GetOrderForViewingHandler.php to add the zipcode/postcode in the trackingUrl variable.
This works, however I cannot find the way to override a handler in the overrides folder.

The documentation only speaks of overriding backoffice views not overriding the query Handlers itself.

Any ideas?

BTW in the Netherlands its very common the have the zipcode/postcode in a tracking url.
Would be nice if this was added in Prestashop.