KitKatsFTW over in Europe has developed a simple solution: a site called "WoW Mod Search," which uses Google's custom engine to search through the four main WoW mod sites: WoW UI, WoW Interface, Curse, and WoWAce. The site is simple, unobtrusive, and aside from some google text ads, there's absolutely nothing to get in your way.
I use Inquisitor on Safari to quickly use shortcuts of any search engine without actually visiting the website itself first. If any of you out there are also using Inquisitor, or any similar search plugin, you should be able to just copy and paste this search url into your plugin preferences as a shortcut for quick access to WoW Mod Search later. (The "%@" in that link represents the space that will be replaced with your searched keywords when you use the plugin.)