I think you can use a generic 5V adapter, so long as it gives you 1A or greater. The only issue being getting the correct low voltage output connector size, of which more below.

A bit of crawling around amazon reveals the spec of the AD-14 adapter to be:

Input Voltage Range 100-240V/50-60Hz
Output Amps 1.0A
Output Voltage 5V
Sleeve/Tip Configuration Tip: Positive, Sleeve: Negative
Manufacturer Part Number ZAD0014D

Then stumbled across http://taperssection.com/index.php?topic=150794.0 which suggests:

Zoom h4n / 5v / Size B, 4.00mm OD × 1.70mm ID / Center pin (+) Ring (-) / Normal Polarity

4.00 x 1.70 is a little smaller than the popular plugs but not unknown - my local supplier has the things http://cpc.farnell.com/_/777-343/1-7mm-dc-power-plugs-sr/dp/CN05722 , A lot of the generic supplies have a selection of plugs so your luck could be in!
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John Allcock