We had the same toilet in our 1998 Sterling Emerald. We liked the system and find now having to remember to fill the flush tank a real pain!
If you have no flush tank mounted on the wall behind the toilet, then you have no flush tank.
As you have no tank, there is nowhere to put the Pink rinse aid.It does not actually "fill" automatically, it just uses water from the Aquaroll as required.
The Pink is not essential. Even though we now have a flush tank, we still do not use it. Think how much you will save by not using Pink stuff!