Ron,
Both of those holders you pictured are designed for Blitz style jerry cans.
They work by clamping onto the metal LIP that is on the bottom of the can and one of the outside handles on the top.
The Scepter plastic cans have smooth rounded edges with no LIP available to clamp. Same goes for Wedco / NATO style cans.
You would need to use a tray, shelf or cage style holder that will capture the entrie base of the Septer can.
There are a few options out there including a holder made by Adventure Trailers - Wil did a write up.