I've come across a nice substitute for a satin cami. The manufacturer is Players and they make nylon-tricot undershirts for men. They come in a variety of colors and are made in either a t-shirt or tank top style. I've seen them priced from $7-10 (US).
They aren't as nice as a satin cami, but for those on a budget...the price is right

. They still feel silky against the skin and covers the tell-tale bra signs fairly well under a cotton button-down shirt.
It used to be easy finding Players brand a few months ago, but they seem to be hit by the current economy...the only place I found them is here:
http://www.chockcatalog.com/item_detail.php?item_id=86BTW-is there a spell checker somewhere in the post editor that I am just not seeing? Even though english is my mother tongue, I am a horrific speller