Simon, when rescuing River in Serenity, also wears a lab disguise in addition to his Alliance disguise.
More after the break...
One more screencap:
This was at the Propstore for awhile:
This is not Simon, but this screencap of the lab tech in the first scene with Simon and River show that the footwear is probably Crocs.
More on the lab techs later.
My Photobucket Album for Simon.
Serenifly Costumes site for Simon.