wow! that's going back some years! Haven't seen one of those for many years.
It was a roll back roof made a company called Webasto - not sure you'll be able to acquire one unless it is from a scrap car but doubt the condition after all these years would make it useable and water-tight
I would think that a simple 'remap' of the Engine ECU would sort it out but shouldn't be doing that on a new car so I would throw it back at VW and says its dangerous and see what they offer
I believe the water pump is externally mounted from the timing chain assembly (but please do check) in which case it shouldn't need routine replacement as it would do if it was belt driven
I would take it back to address the issue with them - if they were willing to acknowledge the fault and replace components then the liability is with them
However it could just be a case of reprogramming the vehicle electronic systems to resolve this issue?
Is there a side panel at the end of the dash that can be removed?
It may only be able to be removed from the rear, behind the dash - maybe able to view it better if the glovebox / lower dash is removed
The first place I would start is the battery condition and security of connections, etc
It is possible it could be reading the wrong voltage if it needs to be programmed in
Try eBay as a starting point
https://www.ebay.co.uk/b/bn_1838652?toolid=20012&mkcid=1&campid=5338906902&siteid=3&mkrid=710%2D53481%2D19255%2D0&customid=