Teardrops n Tiny Travel Trailers

Granted, I've only looked one day for Blue or Pink Foam board but I have to tell you it's not looking good. Looked at 2 of my local HD and one Lowes and they had little to none. I can order extruded board 2" X 4' X 8' for $39 from Lowes or buy Tongue and groove from the store (2" X 2' X 8') for $20.

I will continue looking of course.

Have faith in purpose ... it does require some shopping around ...

You might also try looking at commercial builders supply companies. There also seems to be some seasonality to it, as things start cooling down, the supply seems to grow. My local HD seems to order in big lots in lots of different sizes until they run out (or almost run out) of the different thicknesses and then they order more. Seems like the 2" disappears first.... HMMMM maybe some quiet foamie builders in the Reno area?????
Add to that the climate and they may not stock it much at all. I live where it gets cold so lots to be found. The south and southwest maybe not so much... Not sure where you live

Roofing supply companies may also be a source.

Cheers,
Norm/mezmo