The very short answer is that they don't exist.
A polar diagram for a small boat, especially one that can surf, is all but useless. There are too many variables to represent on the graph.
Boat speed is a function of:
- wind direction
- wind velocity
- crew weight
- boat weight
- wave state
- wave state orientation
- boat set up
Last but certainly not least:
- crew skill
A polar diagram only takes into consideration the first two.
The H-20 diagram in the Hobie U book is merely a representation - it is not based on actual measurements.
You can create your own polars with a GPS and a program like GPS action replay. This is one from my 17 in about 5-10 kts of wind:
You can see that most of the sailing was windward / leeward (it was the last two races in a regatta last fall). The reaching portion of the graph isn't fleshed out.
Interesting that it shows I could sail faster and deeper downwind on port tack.