multiple search instances

Hi,
I’m looking for an extra search box for the backend, indepentely form the search engine in the frontend. Also it must search in custom fields. We use Extended Search plugin because of the broader possibilities. But it gets too slow if we let it search on the specific fields we use in the backend. So we would lik to have a fast search for the frontend, and at the same time a specific search engine for the backend.

Multiple instances of Extended search would be a solution, but this is too difficult. We are looking for a more simple solution.
Thanks!