The Sears low-profile jack is cheap and fits under the rear jacking plates or the rear "Bentley" spot on my BSX 986 which is about an inch lower than stock.
The problem with this jack is that it won't go high enough to get the rear jacking points over jack stands! I use 2 hockey pucks on the jack plate and then can raise the car enough for jack stands. It's crude but effective. This is a portable jack. It is 3.33 inch in height at the pad.
I just bought a really nice low profile jack from Griots for about 400 bucks. It is SUPER low profile and jacks to 20". It also weighs about 100 pounds so it is not portable unless you're a moose at the gym. It rolls incredible smoothly in any direction owing to a huge iron ball built in to it.
Sears jack $49
http://www.sears.com/shc/s/p_10153_12605_00950165000P?keyword=low+profile+jac k
Griot Jack (not portable) $400
http://www.griotsgarage.com/product/in+your+garage/jacks+%26+stands/2-ton+floor+jack.do?search=basic&keyword=jack&sortby=newArrivals&page=1