We're in the same boat, I have a Concentra drug test/physical coming up as well. Found the below gem on another forum, and already did some sewing, good luck:

I, too, am having a combo physical/drug screen and read some words of wisdom someone posted a year or so back. My fear, like yours I am assuming, is that the physical will require a hernia check and you would have to drop your pants and underwear (where most of us hide our sub bottle - and it drops to the floor = busted).

The poster said he buys three pairs of tightie white underwear. 1 to wear closest to the skin (unaltered), 1 on the outside that has a "pocket" sown into the inside crotch area, and 1 to destroy when making the pocket material.

He said he cuts along the seam in the taint area of the 3rd pair, then makes another cut about the length of the bottle toward the back side. Sew this directly on to the same region of the 2nd pair and leave 1 side unstitched (I leave the seam area unstitched). The last unsewn side simply sew from the outsides in until you have a "pocket" large enough to easily access the bottle to and from your underwear when in the bathroom.

That way, if (and it is very unlikely) you have to drop your pants, the unaltered pair closest to your skin will be all the doc would see. The pair on the outside that has the pocket sewn in drops with the first pair and hides the bottle in the pocket. You have the pocket tight enough that this motion doesn't cause the bottle to accidently free itself and run for the door.