The Rialta is built on the VW Eurovan (North America) cut away chassis but it is known as a T4 in Europe so depending on where you are looking for your fuel pump you have to start with the appropriate model. It is further complicated by the North American models had the VR4 gas engines that Europe did not requiring different fuel pump than say a diesel T4/Eurovan.
Some useful links at:
VW T4 Useful Links
Since VW has really abandoned the NA Eurovan market you will likely have to source a new (or good used) fuel pump from a independent VW mechanic that works on Eurovans and old VW Vanagons. They are available but not likely from NAPA. I do know of a couple of mechanics in Vancouver BC since I had to go down this road with my 92 Eurovan for other parts. I did source a new fuel pump that I carried as a spare (never needed it) for a South America trip 3 years ago. Ended up selling it back to mechanic for a restocking fee 6 months later. So I effectively rented an insurance option
when I asked my mechanic what specific spare parts I would need that are hard to find if it were to fail in SA, Fuel pump, radiator cap, and wheel bearing was the list.