I have found a source for Readi-Board at the local Dollar Tree stores. I purchased three sheets of it to experiment with. They have a slight warp that I will try to get out (I will have to experiment with weighting it down). I am not sure what glue to use, I will try titebond III first. Now to decide on which plans to use to get started ....
https://www.dollartree.com/catalog/search.cmd?form_state=searchForm&keyword=Readi-Board&x=17&y=4
Good deal, you will love this stuff once you get used to working with it!
Do not worry about the slight warpage because ALL foamcore boards get this, especially if its along its longer side. This is actually not bad, since if you cut the wings right you end up making this warpage into elliptical dihedral, which is a net gain.
Also, even if the warpage ends up running fore and aft, it will disappear once you glue the chord to the body tube. Now, you may want some weight when you do this, but not much, or you may end up crimping your body tube. I recommend a phone book or two, this gets plenty of 'down weight' but also spreads the load as to not oval your main body tube. The other helpful deal is to assemble and insert your motor pod inside the gliders BT before gluing the wing on (assuming a large delta planform, which is why you got Readiboard in the first place).
Also note that when you purchase this stuff, it comes in a case of 50, and if you end up seeing it half gone, the sheets that are loose in the front are always warpier than the ones pressed together at the rear, so always get sheets from the BACK of the case if you can! Even at this, they will tend to inherently warp some if sat alone for a while. Like I said above, not a big deal.
I use regular ole wood glue on this, since the outer skin is actually more 'papery' than the clay based coating of standard foamboards.
Lastly, I have noticed that Readiboard has had several slight weight changes over the last 5 years, with some of the newer stock being lighter and therefore more desirable. Try to weigh your new sheets, if they come in right around 4z each (150 sq in/z) then you have the good stuff.