At less than $2/2€ each in bulk amounts (and five to ten years of storage life in them), you could probably hoard a lifetime stash of CR2's for your camera for much less than you'd have to spend on that elusive battery adapter...
And rechargeables are a serious option too, if you only get the right ones. The most widespread ones arguably are useless, being intended for storage buffer applications, with a mere 200mAh and a discharge pattern entirely useless for a intermittent high-power device like a camera or flash. But flashlight vendors (like Ultrafire) also offer regular CR2 drop in replacement high power cells that have 600-800mAh@3V (about 70-90% the capacity of good single use ones) - these need the appropriate 3V charger, and have limited storage life, but if you recharge them after three months even if they were not used, they are fully adequate. Warning: There also are 3.6V (or 3.7V) cells with the same physical dimensions - these are not suitable for the Contax (and their chargers would damage 3V rechargeables, too).