I really like the sweeping needle of this analog spotmeter, but in addition to the 9 volt for low light levels, it requires a E640N 1.3 volt mercury battery, which is no longer available. Options seem to be: 1. Use an alkaline 1.5 2. Use a Wein 1.35 with a spacer of some sort 3. Use a hearing aid battery with an adapter Does anyone have any thoughts on what works and what works best? Thank you all in advance.