OK. here's the good news.
A step down transformer is really a very simple solution. You plug one end into the wall socket and plug the light into the outlet on the transformer. The only thing that is important is that the transformer is big enough for the load.
NOW The Bad News.
I've done some more digging on the technical data that you will see at the back of your manual (it's online) and the connected load of the 600RX is **1500VA** This means that a 500W transformer *isn't big enough* - - it must be rated at least 1500W.
THIS IS VERY IMPORTANT INFORMATION. **DO NOT** BUY "ANY OLD TRANSFORMER". YOU **MUST** MAKE SURE IT HAS A HIGH ENOUGH RATING FOR THE LOAD.
You are going to need either two 1500W transformers or a single 3000W transformer with two outlets
Unfortunately the cost goes up........ I see the 1500W is out of stock at this store. You COULD buy a 2000W unit instead. It doesn't matter if they are bigger than the load, they just mustn't be smaller.
You may find step down transformers cheaper than the links I have found. Any 240-120 step down transformer will work *provided* it has a high enough wattage rating.
I have had a look through the manuals, and there is no "voltage selector switch" unfortunately on the lights, and thinking about what these are doing - charging the flash etc, I suspect the power circuits are dedicated to the voltage. Please totally ignore Steve's advice to try running them in series. (Sorry Steve) this is NOT a safe suggestion.
If you have any doubts, or are not sure, please take my post to your local electrician and get him to confirm what you need.