did wonder about some ordinary fittings and pipe normally used for other purposes. There is a nominal 5" dia. thinwall PVC electrical duct that is made in black (and some other colors). Exact diameter is 5.30" and the Valterra is 5-1/32" so the Valterra saddle would be too small.
Yes, the Valterra saddle brackets would be a tough fit on standard pipe. A standard clamp/bracket for a 5" pipe would be a good fit for the Valterra tube as the difference in diameter is negligible -- 1/4" in diameter. That can be taken up with tape or shims for an exact fit.
For the price and convenience, I'd suggest to use the square fence post cover. You can even have a 4" (nominal) PVC gutter inside to use as a drawer when storing or a ramp when in use. I have mine attached to the square rear bumper, now, but plan to sling it underneath after a planned drain makeover.
