My choice:
Shunga roll, made using a wrist support, knee strap, rubber bands. Cheap, Google it for instructions, it's on thunders.
It has stealth, comfortable, used for 6 month on/off. Flaccid hangs thicker. Wrist strap is critical in design, some brands will not work, but it's available everywhere online.
Runners up:
1.The captn wench can be used for ADS, the cable clamp is the only thing that sticks out, (If anybody has a another type clamp that is quick to release and smaller profile, it would be my first choice). Also it can made smaller by reducing size when building it.
2.Elastic wrap, simple cheap ads.
Finally:
A recent medical journal noted gains using extenders but there is a problem:
I cannot wear my X4 labs extender, very difficult, slips off, painful, not stealth unless pants are extremely baggy. Never gained because I could not wear it. Not going to spend anymore money on PE stuff after this.