While it wouldn't work too well in work attire, I carried my Kel-Tec P32 all summer with the belt clip. I wouldn't mind trying it with a P11, either. I might try to make one for my new Walther PPK/S that extends from under the grip.
There's something on gunbroker.com that is like a Hogue slip-on with a tuckable clip, but it looks like the clip would be right under your hand, which wouldn't appeal to me too much. I'll look for it again tonight and post the link.
Another option is the "thunderwear" thing, but I don't think that would suit me, either.