The LEDs are to be driven with a constant current of 700 mA. The coolers require about 0.8 Watts each at 12 VDC.
I used to design LED drivers from scratch and building a 12 V power supply would be easy. However, such devices are now available commercially at competitive prices.
Each LED “head” contains seven LEDs in series driven at 700 mA with a total voltage drop of 7 x 3.1 V = 21.7 V. Two heads in series result in a voltage drop of 43.4 V and a power of 30.4 Watts. A fully enclosed power supply was available with a capacity of up to 48 Volts and up to 35 Watts