I have a Dive Rite Mini Classic 10W HID. The Mini Classic is not even listed on the DR website, nor in their literature. I got it back in Jan, and it was supposedly brand new and just not on the books yet.....but it hasn't appeared, so I'm wondering if they decided not to mass produce it? Anyways, it's the same as a Classic, but half the height. The canister is smaller than the MLS, but with the same battery size(7ah). It provides, according to DR, a 6 hour burn time, but they recommend no more than 3(half of the battery life to avoid damaging it due to excessive discharge). I've used it for 4.5 hours in one day, and checked the battery voltage and it was still above the minimum required under load.
Dive Rite now has what they call a "Half height" Wreck canister. It is truly tiny, about 3-4" diameter and 4" or so tall. It is literally half the height of the Wreck1 canister. You can get NiMH(Nickel Metal Hydride) batteries for the half height, and I would assume for the Wreck1. The NiMH batteries for the half height provide a 4ah battery, where as the gel cell for the Wreck1 is a 2.8ah. That means, to me, that you could likely get an 8ah NiMH battery pack into the Wreck1.
Either the Wreck1 or half height wreck are what I would recommend if you want a 10w HID. My mini classic, while smaller than most other canister lights, is still a bit large. I am now considering changing it to an 18wHID, and buying a half height wreck canister to put the 10wHID head on. 4 hour burn time on such a small package is pretty impressive.
Check out the following portion of Dive Rite's website for more info on the NiMH and half height Wreck canister. The picture at the top left is the Wreck1(on left) and half height Wreck(on right).
http://www.dive-rite.com/products/mls/nimh.htm
Mike