Vintage synths rarely use AC adapters, so I wouldn't have expected you to find one in a music shop. I think Radio Shack has a 400mA one. That might work for you. I'd think Chinatown would more likely be a wild goose chase.
I believe a lot of them are used for stuff like routers and desktop computer speakers. Generally you won't find spares for sale other than ebay, etc. If your time is more valuable than some extra money I'd consider mouser.com or a similar electronics giant that can next day ship. You'll be spending plenty shipping overnight but you'll not be adapter hunting when you can do something else.

--- In Doepfer_a100@yahoogroups.com , Richard Francis <rf@...> wrote:
>
> Hi there,
>
> I'm in New York City for a week or so and am trying to find an adaptor
> to get my 3 x Doepfer modules in minicase working over here (I'm from
> New Zealand i.e. 240v).
>
> I need a:
>
> 12v
> AC 500mA
>
> I'm finding an ac/ac adaptor is not that common. I've been to two
> vintage synth stores with no luck. Any suggestions
>
> Thanks a lot for any help
>
> Richard
>
>
> Richard Francis-486 New North Road, Kingsland, New Zealand
> www.richardfrancis.net.nz
>