I investigated this also, the outcome of which is that prudent buying of the standard air-zinc batteries was overall a better way to go.
I bought a ‘mystery-pack’ from an online supplier, with a packet from each of a cross section of manufacturers. I recorded the life of each brand, from expensive to cheap Chinese, and to my happy surprise, found very little difference in longevity. Some lasted 9 days, some 8 days.
To avoid them going flat in the middle of work, I resolved to change them every Monday morning regardless, and given that the cheap ones were only about 40 cents each, I doubt I could think of anything that costs me less than a dollar a week to run. And no re-charging.
The price of the batteries varies wildly, with some places charging over a dollar for the same thing, so scout around on the net and you will find good battery prices.