Long life coin cells?

[larangel3]

Where can I purchase coin cell batteries with a lifespan of at least 2 years?

They will be used to power a very small circuit with power requirements ranging around .2 mA

[mikerj]

They will be used to power a very small circuit with power requirements ranging around .2 mA

More detail is needed, what is the duty cycle of the circuit, i.e. the on times vs off time?  If you drew 0.2mA continuously for two years you'd need a 3.5Ah cell which is not going to be anything like coin sized.

Just for reference one of the largest commonly available coin cells is the '2032' which has around 240mAh capacity, enough to power your circuit continuously for about 1 1/2 months.  Any quality brand lithium coin cell would be fine for standby duty for two years (i.e. their self discharge is very low, about 1% per year).