The approach I took to that situation on my LT Van was to buy a piece of flexible corrugated 70mm exhaust pipe from a local motor factors plus a U-Clamp to suit, then cut to the required length. Worked fine.
My Ducato needed a length of pipe similar to your missing bit by the sound of it and I just cut some of the remaining pipe to length, bought another clamp and job done.
Didn't need any special tools for either time - just a spanner to suit the clamp and a way to cut the pipe (I used my Dremel. could just as easily used a junior hacksaw).
Fitted here -
View attachment 64623
If you want a piece plus clamp I can cut a length off if you tell me how long you want it. I should have 400mm left? Clamps are around a tenner (70mm clamps are not that cheap). Not sure how much the pipe is. Will be 1/4 the price of the original (2M length) so I think around £20 but need to check.
Postage for Royal Mail Small Parcel (ok for upto 400mm pipe) is £3.50.
Just an option for a DIY fix
Wow - some off the wall prices on-line.... £200 a metre here -
https://www.thehosemaster.co.uk/galvanised-steel-flexible-exhaust-hose