OK, rewrote this a couple times to try to be clear.
1. The AM21 should have a polarized C7 cable that connects into the power input in the attached pic. This is just a cable, not a power supply, and you can get one from a lot of different places for under $5.
2. You have choices with the cable that's attached to it. You can ignore it. Or, you can remove it if it's bothering you, I guess. Or, you can cut off the connector and attach an outlet to it, and plug the HR54 into that outlet.
One more thing that occurs to me is that if you wanted, you could remove the attached cable, put a plug on the end of it, connect it to the power input, and you've got a power cord.
If I'm still being confusing, call me out on it.