Non-standard exhaust section?

My '83 110 recently developed a noisy exhaust. When I checked it out I found that the downpipe had rusted through just before the flanged joint where it meets the second section. The top joint where it meets the manifold assembly is also flanged, so I thought "Easy, just undo six bolts and whip it out, bung a new pipe in and I'm laughing!'
Unfortunately, I can't find a matching pipe from any supplier online and I'm wondering if it's because this is a conversion from the original petrol engine to a 2.5td Discovery engine, which a previous owner had done.
Can anyone advise? The downpipe is a simple 'S' shape which is fairly easy to see from the photos:

since a disco 200tdi was never fitted by lr to a 90 or 110 front pipe if not the middle will have to be made out of parts

Take it to a exhaust shop. It would be childs play for them to make new 1 for you

The bottom flange backwards looks correct and original and looks like to me, that the downpipe from the original petrol (the bottom bit that has rotted)has been welded to the conversion piece at the turbo end.
The turbo end is the hardest to make a good job of and if that bit is still sound get a petrol down pipe and copy what the've done, ie cut and weld the new downpipe to the old turbo end.
That's what I did for my 2.5nad to disco 200tdi.
You will need to check bore sizes of the exhaust you've got to be sure it's a petrol system so the new downpipe you get is the correct one.
Iirc they are quite cheap so you don't feel too bad chopping up new downpipes!