The temperature gauge is part 255 919 511A and
is available from VW Classic parts.  So is the
fuel gauge.

I'd swear I saw it on GoWesty's web site, but
cannot find it now.

BusDepot lists it for $105.48 as a special VW
order.

You can find VW dealers in Europe that list it
for about 85 euros so the BusDepot has a good
price, as usual.

Richard