What about just a regular recessed outlet? Plug the wall wart in and then hang the telephone in front of it.
I don't know if it'll be recessed enough, but it might be worth a look.

The short answer: I called Panasonic support, which said the Leviton plate will work. I hooked it up, and it seems fine. This saves me a LOT of work.

This is curious, because I emailed Leviton support, and they said: "The 40215 cannot be used with any phone that requires less than the 7.0 minimum." Perhaps they fear liability. The plate comes with several adapter tips, and it's possible to mismatch the pin polarity, which would damage the phone.

Also, Amazon reviewers of the Leviton plate claimed it wouldn't work with the Panasonic phones.

If the phone dies, I'll report back.

TS

I think the question is - what are the voltage requirements for the phone - assuming that they aren't just saying that you have to use the power supply that came with it.

The "5.5VDC" surely doesn't mean that it has to be between 5.49 and 5.51 volts. It the real spec' is 5 to 9 volts then there shouldn't be a problem - the Panasonic rep' might know that - but I wouldn't expect the Leviton one to.

Is your Panasonic cordless phone still working on the lexicon wall jack?
I have the same setup and I'm afraid to hook up my new Panasonic that requires 5.5 volts

As of today, the phone and wall jack continue to play nicely. I haven't given either a thought since my original post. Good luck!