Have to assume as it has the factory bracket then it is not cobbled together as you put it.
just because you have not seen one before does not mean it does not exist, pretty much every day I learn something new on this forum alone.
I remember first time I saw a small metal fuel filter in the same location as the ops sedimentor but on a early 90, again not seen one of them before.
The pics posted are not OP's...he doesnt have that set up...
It absolutely is factory and not cobbled together! These are even shown in the parts manual and attributed to vehicles post Suffix-K. The desimenter is designed to take the bigger lumps of crap and water out of the fuel before it gets to the fuel pump, which doesn't have a glass bowl in this application.... and under the floor at the front is the correct location for vehicles with fuel tanks under the seat. It was the mounting bracket I couldn't make out exactly from the parts manual - I could see a rough shape of half of it, but the pictures supplied above are brilliant. Whether I can actually find one remains to be seen.... looks pretty unlikely at the moment....
But if you dont have it that means it wasn't fitted so why are you fitting one...