I am having trouble locating good dealers to supply the above item
(Lowe's seems to carry just one size).

We have several old-fashioned awning-style windows let into our
concrete foundation that are relatively close to grade.

I would like to dig out a shallow well around the foundation, surround
with a steel corrugate semicircle, fill with gravel, and then cover
with a plexiglass or polycarbonate bubble.

Despite multiple tries at google, I haven't found many dealers of such
on the Internet.

Any suggestions?

Thanks