Well, I felt like using some of my experiences, from my 'open-bottom-jeans' on a brand new pair of trousers.
Thus i went to the library, a brilliant source of knowledge by the way, and
got me a relevant "Burda Fashion Magazine", number 12/2007, in which I
found a pair of trousers, no 113A, which I found to be perfect, for
modification.
All I needed to do, was to 'shrink' the hips a little, apply a hole, in the
right spot, and finally to move the zipper to the backside of them, in order to
avoid all the razzmatazz of zipper and button, on the front side, where I
believe to have something more relevant to show..*S*
Next I went to Stof 2000, and purchased some stretch fabric, (this one), a zipper (1 foot long), and then I started cutting and sewing, upon which I got busy making 'acessories'.. *G*

The trousers 'on their own' front and back.

With belt-purse (cock'n'ball-purse).

-and a little sensation - at least in my world - I succeeded finding and sewing
transparent PVC...
I'm quite sure, that you'll see this material again, in my homepage - not at least as I have also discovered where to buy 'invisible' sewing-line...

An improved fashion of the triple ring, with a 'base ring' added, to keep it all
together.
The modified triple ring, without cock'n'balls.
Here with the 'base ring' (latest addition) at the front.
Here with the bottom cock ring at the front, and the ball rings upwards.
Here with the bottom cock ring facing left, and the ball rings to the right,
standing on the base ring.
Here standing on the base ring, facing the cock ring.
More options, here with the shorts-edition of the trousers...
The 'gadgets' are (of course) interchangeable - they fit the trousers as
well as the shorts.

A silvery cock'n'ball holder, just for the sake of variation.