It looks like you're in a spot.
I can't find 46781894 ever had any successor part numbers and the item has vanished altogether from the Fiat
ePer so it's tricky to find another compatible OE part number that could show up on some part manufacturer's compatability list.
"50393" doesn't come up on the current Birth catalogue, even though it must have existed at one time... and Malo's web catalogue doesn't recognise their (presumably obsolete?) 149095 part number either.
The 50842 probably looks the same as yours but it must be subtly different at least, otherwise it would be listed as fitting your car (Birth does not list a mount for your car).
Having said that it might be close enough that it can be modified or tweaked to fit.
As far as I can find out, the dimensions of 50842 are as below, though I don't know which bit of the part they relate to. You can measure your old one and work out which is which;
Diameter 1: 20mm
Diameter 2: 13.2mm I guess these are the holes for the bolts
Intermediate length (maybe the length between bolt holes?) 143.3mm
Overall length: 218mm
Shore (no idea at all what this might be): 65 +/-5
Ralf S.