Sprung a leak

I fired up my 1986 1.8 gti today, left it running for a few minutes when it sprung a leak spraying water and steam about.
The coolant system has a hole in the metal pipe that is part of the pipework connecting the coolant header tank to the
water pump.
If anyone can provide me with the  part number and description I'd be very grateful since my online searches so far
haven't met with success.
Thanks folks

One that looks like this sort of?



VW mk1 heater by-pass pipe.  There are various one for cars, but need  to know if you have a oil cooler installed.

One type

https://www.werk34.de/en/metal-cooling-water-pipe-121.055.065-m.html.

Diagrams available online suggest you need 055121065M (ignore the information in the earlier version of this post which was incorrect).