This vintage SWR meter made by Swan and marketed under various badges (like the Quement unit shown in the picures) is one of the best compact units I have ever encountered.

It works well for me on 160 Meters through 10 Meters. I have used it in a pinch at 6 and 2 meters. I have used it on HF at the 600 Watt level and 150 Watts AM with no problems.

It is NOT a true POWER meter, it is only relative power. Its primary function for me is to view forward and reflected power simultaneously while adjusting a transmatch. Switching a single display back and forth just does not do the job, as the adjustments interact highly. You must maximize forward power while simultaneously minimizing reflected power. This unit was created long before cross needle meters were available, but it works every bit as well.

I repaired this unit with MFJ replacement meters. I got it free at a swapmeet. I have other identical units with the original meters, but I find them so useful to monitor transmitter performance that putting one of these in the output is cheap protection for the radio is a good idea. I liked the Quement electronics model for nostalgia, since I used to shop at their store in San Jose, California, in the late 60s.

You could replace the sampling line with a modern toroid based sensor which would be a true power reading. A 100 Watt class unit would be easy to make. The dual variable resistor could be replaced with a compact range switch, and internal screw driver adjust calibration resistors for 10 Watt/QRP and 100 Watt levels. This is cheap enough at swapmeets, it would be worth your while to pick one of these up, just for the case and meters, which would make your project more affordable and attractive when complete. I may modify one of them and post the results later.