The "new" sceptre gas cans are meant for adapters that use the external threads of the can, however they also include the internal threads which the old cans had. As such, you can use the various old adapters or you can go over to the newer accessories and adapters that utilize the external threads of the can.
The older "spout, can, flexible) will work, but as most of these are getting quite dated, they do not lock in as well as they used to. Add to that the threads run way into the can, whereas on the old cans, they ran in maybe a half inch, which allowed the rubber seal of the spout to expand beneath the threads and better lock in.
I just got a legful of diesel two weeks ago when one of the old spouts decided it did not like me applying pressure on it while pouring. When you do get a new style spout, you have to watch that the O ring inside is there. They do tend to break and vamoose over time, then you will get leakage down the spout. In the cold, you can also get cracking of the flexible part of the spout. I have one or two out in the sheds where I had to cut them short to get rid of a break.
Perhaps the best spout to get are the old metal style that are threaded as opposed to having the rubber block that gets compressed.
https://www.combathunting.com/CLEARA...Can_Spout.html
There is a downside to using surplus new style cans. The scepter containers have a breather tube inside them that allows air to come into the can while pouring. Often the tube inside will detach, at which time the can is technically scrap. You will see the little breather hole on the top of the opening of the new can. Without the tube, they will leak a bit from that hole until the can develops it's negative pressure. You won't get a leg-full of fuel, but you don't want to be wearing your Sunday best either while refueling.