There is a company in UK called 'The Small Battery Company' (Google the name) They sell a tiny device that fits into the battery compartment of cameras that used the defunct Mercury type. This device is then fitted with a suitable 1.5 silver cell but the voltage is reduced to 1.35 volts, the same as the mercury ones. There are alternatives such as the Wein Cell which also produce 1.35V but they are not cheap and do not last very long, or you could have the meter re-calibrated to handle 1.5V instead of 1.35V, but this could also be be expensive