I have a DIY 8V pack, made from a more or less ordinary 6v gel cell battery, about 5Ah, and a more unusual Hawker Cyclone 2V gel cell 5Ah strung together to deliver 8V. I use it with a sunpack hammerhead or my metz 45 unit. It hangs from my belt. My Quantujm was gifted to me after I made the DIY pack. Prior to getting the Quantum and its charger, I charged the thing off a mid 60's Braun Hobby EF300, which also ran off of an integral 8V pack.
If it is a studio style offering you want, look to computer switch mode power suppllies. I had a slew of 6V 4aa cell flashes I began my studio work woth. Lots of zip cord, but I powered them off of an old PC power supply. It was happy to deliver 20A at 5vDC, and recycled theflashes quite quickly. Faster that after alkalines recycle after bing used a few dozen times.
So an adjustable DC power supply set at 8V to source up to about about 10A would do fine. Scour you local electrincs wholesaler or turn to the web.
I've been looking for the same thing. I was thinking of using my quantum adapters at the flash end with a 9v transformer as power source (with appropriate jacks in between). But I don't know that a common transformer of the appropriate voltage provides enough amperage. Though I'm expect it would not be too much a task to build one.
One thing to be cautious about is the contacts between the flash and the Metz battery holder. There are 2 different "plus" contacts and a single "minus". The 2 different "plus" contacts are different in the AA alkaline holder (9v) than the nicad (7.2v) holder. While it's not explicitly stated, I'm pretty sure his approach assumes use of the Metz Nicad battery holder.
But I might use a battery holder and individual NiMH cells. The reasoning is that if an individual cell fails it can be easily replaced. The disadvantage is that you lose the more reliable soldered contact between the cells.
The contacts on my Quantum adapter match the contacts on the AA alkaline holder; which is consistent with the output voltage on the Quantum Battery 2. So I think I would want to use 8 NiMH cells for 9.6v.
Another approach would be to buy a dead or dying Quantum Battery 2 and replace the internal 8v battery yourself.
My quantum came with a battery doa, and I had to mail order after not finding anything 8V and size wise compatible at my usual haunts.
Under $60, as I recall including shipping.
I have heard of problems with the springs in AA holder overheating and loosing their spring temper in the process when the flash is fired at a fast rate, empowered by the fast rechahrge from NiMH cells.
I stay clean of NimH due to their fast self discharge rate. With lead acid gel cells I can recharge them after using them, and then they can sit on the shelf for months before I want to grab them and put them into service for a shoot. They are always still close to full chahrge. You cannot say that after a NiMH has sat for more then a couple of days in my experience.
What is the purpose of avoiding the use of a Quantum? With a Turbo, I could fire my 45CT4 at full power about once each second at a wedding (I didn't fire more than a burst of 2-3 shots, for thermal considerations of heat disspation in the flash).
Well, it costed me Euro 50(Battery + Charger) and 30mins of time. I shoot mostly at home events with metz as main flash with an umbrella and 430Ex II to lit the back ground.