Hi,
Digital Oceans basically phased out aquarium products a couple years ago. They manufacture products for another industry, can't remember which one and decided to focus only on that industry and to discontinue all aquarium products. So they are not available anymore, unless you just happen to find some old ones instock, but problem then would be service/support if you had problems.
So right now, only dimmers available that i know of are Solor Dimmers for the IceCap VHO's. Haven't seen anything on halide, although Icecap had a 400watt Icecap Halide ballast that was 50% dimmable standard, but they are revising it right now, so not sure if it will have these feature on the revised one or not.
thanks
jason