I bought three of those directional couplers on eBay and they work very well for measuring PA output power.
The coupling value can be selected 10/20/30/40dB. (and some more)
Those directional couplers are sold by many sellers and also on amazon & Co. for a few bucks.
At "Antons Funkperlen" website are photos from the inside: http://funkperlen.blogspot.com…htkoppler-fur-7-euro.html
Edit: attached a picture of a measurement on my 30db coupler