I purchased all the materials needed from Lowes - except the orange swivel fittings (2) that I use with my regular sewer hose. Don't remember the exact names or sizes but it was not hard to pick them out. Goes together very easily and comes apart when you need to move the trailer for any reason.
Edit: Forgot one of your requirements. This
Flush King would attach to the 2nd orange colored clear angle in my pictures below. It will swivel to any angle you wish and, along with the other orange clear angle fittings, allows the long drain tube to be raised up and/or rotated outwards as much as you need to reach the drain hole.
This is also possible with the pictured fittings.
I have used the Flush King many times and find it does a fair job of rinsing out the tank but the best way to clean your tank still remains the good old "down the toilet" wand.
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine