Van-Cafe and Vanagain repop it, but until they took the time and trouble....

1.9 H pipe (and looking at the Van-Cafe repop, it does not function as the
original plastic pipe did. I think Ken Wilford has a repop that is closer in
function. If you look at the plastic part, you'll see that it is designed to
not have the header tank be in the coolant flow.)

and only available on the used market:

1.9 upper thermostat housing

Jim