I have had a good amount experience with housings for the Canon line and especially the HV20 and HV30 camera. I would definitely recommend the Ikelite unit; part #6071.
http://www.submergecamera.com/ikelite-unde...camcorders.html
At this point you are only going to find maybe 1 or 2 other options for this camera besides the Ikelite version, while all housing manufacturers attempt to build a great housing there are actually only about 3-4 that achieve this goal. Ikelite, Gates, Light & Motion and Ampibico are the best in my opinion that build housings for multiple cameras. Of these, only Ikelite has a housing still available for this camera.
Here are few items that set the Ikelite unit apart from what is available:
1) Size & Weight--Ikelite unit is 9 lbs, other units are around 15-16 pounds but then for it to actually work you need to add an internal lcd which adds another 2-3 lbs.
2) LCD monitor viewing-- Ikelite offers a side mounted LCD mirror, on models like this (more affordable price point) I do like this feature because you dont have to worry about batteries and possible failures on an important trip.
3) Access to controls-- Ikelite offers almost full function of the camera, this is important because if you are shooting HD you want to be able to access the White Balance, less popular housings will offer this as an option at an extra cost.
4) Ikelite is time tested as a great unit and at Submerge Camera we only feel comfortable offering only the best brands to our customers
Hope this helps and let me know if you have any more question.