Zip Code Search in WordPress

Hey,

i would like to have users searching via zip codes the nearest shop to their adress. So something like a mini adressbook, but i think a plugin or external script would be to much for this.

i thought of adding 10 pages with each one postadress and then writing the zip code additionally into a custom field. it should be searchable via the installed plugin “search everything”, but how would i make sure that it would be really the nearest shop?

do you have any ideas? thanks in advance