I'm fairly sure any of the 16v pipes from a VAG car of that era would be OK. The difference in the pipes from the others can be the way they are routed around the engine and also the position of the inlet/outlets. Some of them are pointing in the wrong direction e.g. WUR and dizzy I think are in the way.
I have a second hand 027 121 06 K from the early valver but that has an extra outlet over the P. This would involve changing the outlet on the block to the early type yet I'd still be using an old pipe. It is the same dimensions (i.e. length and bends) for the K and the P.
I've heard a MK3 16v pipe will work but it goes over the oil filter, involves some bending and some of the other water pipes too. Not ideal.
If there is a good plumber, good at making pipes you might make a nice profit here.