Stretchers apply constant tension to your penis for a prolonged period of time without using weight. I'm not wildly enthusiastic about any of these devices.
This is inexpensive and easy to make, as well as inconspicuous. It is awkward to put on and remove. Only material needed is a 4" (10-15cm) wide Ace (sports) bandage.
The inventor of the Penis Plus deserves congratulations on a clever design. Alas, the price tag of DM 298 (~$US 160) invites you to make your own at a fraction of the cost. (The original is at www.penisplus.com.)
The concept is simple - pull your penis to the side with a belt running around your waist, anchored to the base of the penis.
All you need is an ace bandage. Tie a simple knot to secure the ace bandage to your penis, run the bandage around your waist and loop around base of penis. Tie it off using a taut line hitch (see below) and tighten as needed.
After you do it once, you'll see why some extra padding is a good idea. So, before tying the end of your penis again, wrap a piece of cloth around the penis a few times (I use a short piece of the Ace bandage).
To make this work, you need to know the taut line hitch - a knot that will serve you in many other ways (great for tying down loads on cars, for example). This is how you tie it using the swim cap:
Here's another diagram (thank you, Boy Scouts!):
Leg strap ('Hiker')
This cheap technique is awkward to install and remove, but requires only some string and an attachment device (see Heavy Penis Weights)
You can wear this while walking, or tie it to a fixed object for use while sitting at the computer (wearing shorts or bathrobe makes this easier).
Tie string or other strap strap around your leg, below your knee. Tie a string to your attachment device (loop, tape, swim cap). A cord lock (from camping supply store) makes tension adjustment easier. You can also probably do it all with an Ace bandage. I haven't tried.
For public use, you'll probably (!) want to wear long trousers.