That one's mine if you want it!
From the vast amount of brick walls I ran into, Shop4Parts had 11 of these in stock when I enquired a month or so ago (the other pipe) Fiat Parts, Fiat Spares, Alfa Parts and Alfa Romeo Spares Alfa Romeo GTV Oil Cooler Pipe
and they also carry the cooler itself Fiat Parts, Fiat Spares, Alfa Parts and Alfa Romeo Spares Alfa Romeo GTV Oil Cooler
and they were the cheapest prices I found.
As far as the discontinued pipe is concerned, I think I have the last OEM one in Europe tbh but I did get a quote from afra.it in Italy for one for €155 delivered (see pdf) but didn't follow it up.
Other than that, the only other advice I've been given is that the solid parts of the pipes are generally unaffected and it might be possible to get a company like Pirtek to remake the bit that goes rotten, provided you have time and inclination to get the pipes off the car and give them to them. I assume this is what Autolusso are doing.
This will probably still mean you need a new cooler radiator, however, as the rad is alloy and the pipe fittings steel and they fuse together so when you get a spanner on them the lugs just snap off the rad rendering it useless. There's some speculation on here that you can cut the old fittings off the rad with a dremel, or similar, if you're careful, but then you wouldn't have anything to give to Pirtek for them to copy so you'd have to disconnect both pipes from the engine and remove cooler and pipes as one unit.
This still leaves the issue that the one pipe in particular is an absolute b*****d to remove from the engine apparently, 4-5 hours labour for someone who knows what they're doing to replace the whole thing, a few days and lots of shouting, cannibalised tools, plasters and skinned knuckles for those of us less professionally adept.
All this and I never actually needed to know any of it...
Hope it's helpful to someone!