We call it shade cloth in these parts. Here is a link to one possible
solution to your problem.
http://www.usnetting.com/HTML/shade-cloth.html

The type of cloth you need or it's density of weave depends on the type of
orchids you want to grow.

I might also suggest you find a local orchid society and start showing up at
their meetings. This will not provide shade for your orchids but it will
advance your skills needed to grow and bloom them very quickly

Your email address makes me wary

"Erik" wrote in message
.. .

I'm a bit of a newbie, but I do have two orchids blooming!

Question: my orchids don't seem to like the Florida sunshine. They start
to turn yellowish, but when they don't get sun, they don't bloom.

Is there a screen that I can buy or something to create a more defuse
light?

Erik