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I'd suggest a pair of polarising filters piggy backed onto each other. These will vary the amount of light getting through according to their relative placement to eachother. Rotate one way, you get about 50% reduction. Rotate 90 degrees and you get nearly 100%.
As the Moon's brightness changes, you can then vary the amount of light getting through the filters. These filters are also good for reducing the glare of Jupiter, even Saturn.
I've got a set of these filters, and are good also when photographing the moon with a web cam. If I'm using my 17.5" scope, I have no choice but to use these filters for visual and webcaming the Moon.
These are readily avialable, and Andrews has 1.25" ones for around $20 each.
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