I’m on a new computer, so I’ve lost all of the extensive customizations I made to my Overview, which is a lot trust me. If I’m not mistaken, I’ve also lost all of my fittings as well.
Does anyone know of a way of retrieving either of these things, any chance they are saved somewhere server side?
Unless you have access to your old computer, there is no way, nope. These settings are stored on the client-side. Log into the game and join the Z-S Overview channel, set that up, and customise it. Sometimes a fresh start is a good thing.
Regarding overviews, I would rebuild it from scratch. If you have been away for about a year you will be missing objects from your overview. Then create a private chat channel, and put a link to your overview profile in the channel MOTD. This is an easy way to share your overview/s with your alts, and friends. It also allows you to use it if you change or lose this computer.