Just picked up a dozen Sony Ni-MH 2500 mAh Cycle Energy AAs.
All NiMH cells have a nominal cell voltage of 1.2V (some mark it up as 1.25V). It's an inherent limitation of the chemical components.
I also found web stores selling 1.5V NiMH Duracell, but they look dubious to me. It's either snake oil or a misprint. If you pick them up and measure the voltage, I'm sure they are lower than 1.5V.
Each combination (NiCd, NiMH, LiIon etc) has its specific nominal cell voltage. See this table:
http://en.wikipedia.org/wiki/Rechargeable_battery#Table_of_rechargeable_battery_technologiesSome equipment will run just fine on 1.2V, but the OP wanted to avoid it in this case.
Like notlance said, your performance will probably be perfectly OK with 1.2V cells.
So he either has to bite the bullet and go for NiMH with lower voltage, or for alkaline rechargables. Well-known brands are Rayovac, Lenmar Charge-Ables and Juice. I've seen them rated 1800-2000mAh. Search Google shopping or ebay and you'll find them. Note that you need a dedicated charger for them.
If you go the NiMH route, the CycleEnergy 1.2V has gotten great reviews regarding the discharge curve:
http://www.amazon.com/Sony-Energy-Rechargeable-Batteries-4-Pack/product-reviews/B000PHMN44I can also recommend Eneloop 1.2V, it's cutting edge technology:
http://www.eneloop.info/home/performance-details/voltage.html