I have a Fantasea housing for my P3 that I bought from Jack just under a year ago. So far it's been nice, but in the newer design (like that for your L12) Fantasea took care of my only gripes with the older design of my housing. These are:
1. to navigate the menu on my P3 I need to rotate a dial then push it whereas in the new design it looks like it has the 5 buttons right there over the menu
2. the new design comes with a threadded lens ring for adding add on lenses
Also (and not really a gripe) the metallic latches and buttons looks more rugged than the plastic ones for my P3.
I can't comment on how well they hold up over time since I've only had mine for about 9 months now, but so far so good. Also, Fantasea housings come with 1 year DEPP insurance againt flooding for your camera.
Yes, you can attach strobes to them as they do have the standard tripod mounting screw on the bottom to allow you to attach a base & arm, even ones from other brands.
Like I said, I got mine from JackConnick (the previous poster). His price was quite reasonable (cheaper than buying through Fantasea) and he's been great with the follow through when I had questions. I'd definitely buy through him again. Matter of fact, since I recently lost my P3 at a party, I will be getting a newer housing from him if I decide to upgrade to a P5000 or 5100 instead of just getting another P3 or 4 for my now orphaned housing.
The only other housing for that camera that I know of is the Ikelite. Since both housings have the same 200ft depth rating and the camera doesn't have a hotshoe to directly attach a sych cable to, the only difference between them is that the Fantasea is more compact and only 2/3 the price of the Ikelite.