See also lockable clothes.
If you have a penis, you can use it to lock your clothes on you (I just love this statement: “If you have a penis, you can use it … ;-D )
Put on any clothes with a built-in condom (e.g. latex pantyhose, a catsuit, shorts) or usual nylon/lycra pantyhose (you may want to add a swimsuit or a leotard) or zentai. If there is no built-in condom (or cock&ball sheath), stretch the material around you not-erected cock & balls and tie shoelace around the base of your penis behind the scrotum. Not too tight and make a simple easily undoable knot.
Then place a lockable cock ring (I found it in this chastity and bondage eBay shop) around the base of your cock and lock it. Then remove the shoelace. Done.
If there is no penis sheath (if you use, for example, usual pantyhose), you can curl your cock into a tight ball, so this technique will prevent erection. But you will also have to pee through the material or wait until the key is available (an additional bonus in some cases 😉
To prevent pulling out, the ring must be as tight as possible, so measure carefully.
You may see a simplified example in the Lockable / Chastity Pantyhose forum thread.
I’ve looked through all you lockable clothes stuff and you don’t seem to touch up on (even briefly) clothes that have laces. These clothes are the easiest thing to lock. That being said most people don’t actually think about how it can be locked. Simply tying the laces with the same knot as tying shoes (that knot with the loops we all know about that you can simply pull the ends and it comes undone) and then putting a lock through the two loops. After this no amount of pulling in the strings will help. And it’s hard to get extra long laces or they are a bit expensive. Just something to think about.