I am looking for a place to purchase a product called, 'Solar Screen'.
It is a clear sheet placed over your stomach when tanning, that gives
you the appearance of six-pack abs after you tan. The man who I
believe invented it is Glen Raymond Harden. I am searching for a place
to buy this product, or a product just like it. Any help is greatly appreciated!

I doubt that this product is still around.

Here is an archived copy of the website that used to offer "Solarscreens":

http://web.archive.org/web/20020120145508/http://www.solarscreens.co.uk/

That archive was made on January 20, 2002. There are no archives since
that date; the domain name is now used by a different company, which
sells awnings and solar blinds.

If you can't find that, you might consider trying stripes of a
sunblocker (zinc-based) to create paler lines on the underside of your
abs.  It could look funny if you got them wrongly placed.  Get a
friendly art student to help you (not one that you want to impress
later)  .-)

You can use a spray on or airbrush tan like those found here;

http://www.lotionsource.com/sunless_self_tanners.html