You will find that a water pan is not needed in either. A UDS hold moisture so well just from the meat you are cooking. A lot of guys just use a pizza pan as a heat deflector. I just buy mine at good will for a buck. Get nasty/dirty throw away and buy another.
18.5 & 22.5 WSM-Weber one touch. Cyber Q Wi-Fi. Head cook Thick and Thin BBQ