Here's a picture of my "no-nose sphera" monstrosity (no I'm not balding, the hairline has, uh, always been that high. Yeah, that's it...

).
I decided to put the tubing through the front, right where the logo is. The mask is very narrow at that point, so don't try to make a hole too big. I then stuck a short piece of hard tubing (I actually used the insides of a ballpoint pen in true MacGuyver spirit) so that it's evenly inside and slightly pointing out of the front. Then I'd glue and seal that up. Then you're basically done, you just need to attach some tubing into the little stump and hook it to your mouth.
I wouldn't know where to get the tubing in your area

But I guess any shop that sells plastic, rubber etc items would do. One idea off the top of my head that comes to mind is pet shops that sell aquariums, their air pumps use tubing that is about the right diameter. You'll want to get tubing that is not too soft (not silicone tubing), because the soft one collapses under pressure and then you cannot equalize (or it becomes very hard).
I find this design good in the sense that because the tube runs through the center, I can put the hose thorugh my noseclip and secure it so it's not wobbling about with the water flow.
For good measure, I added a healthy layer of epoxy around the outside bits to support the whole thing. Not pretty but it works...
The biggest problem was that at first, the tube was protruding a little too much in the inside, so when pressure would push the mask on my face tighter, it would actually seal the tube against the skin in my forehead. While this was actually cool at first (it would not leak even if I let the tube out of my mouth), if you let it go too tight, you would have to use way too much force to get air flowing again, which kind of eliminated the whole point of a pipe mask. But that was easily fixed.
This is just one design, propably not the best or worst, but one trial. It works ok, but I have to say that in the end, I found it less of a hassle to just dive with a normal mask. The whole thing takes so much consentration and makes equalizing the mask much too complicated for my taste versus the benefits...But it was fun to make and is always good for some strange looks when I whip it out
