Glenn Ashmore wrote:

....big box and buying some fresh "blueboard" foam...

Unless you're in [southern] California. Neither the Blue (Dow) or Pink
(Owens Corning) extruded polystyrene is available anywhere here.
Mcmaster-Carr, you say. Nope. Other building supply houses. Nope.
Lowes, Home Depot, Orchard Supply?
Nope X 3. Don't know why, simply not available...

MW