I use an Exercise Pen (aka, Ex-Pen or X-Pen) I got from Amazon, and they shipped it free to Hawaii (which surprised me, considering it's a heavy item).
Midwest 36" Exercise pen with door.
You can easily configure it to different shapes to fit your needs, and if you want to give the bunns some outside time, you can fold it up to take outside and set it up in the yard.
I find an X-Pen to be a better environment than a cage, but if you really want a cage, Amazon has a selection of those as well. Look for larger dog crates, in addition to rabbit cages, because most "rabbit" cages are too small.
As others have suggested, you can also build a really nice enclosure out of those wire cube shelving panels (aka, NIC panels). Avoid the ones from Target (their holes are too large). Get the ones from K-Mart, they have 1.5" holes, and are the best value for the 6 cube set (usually $22.99, but frequently on sale for less).
Aloha from Kapolei! Tim