The best way I've found is to use
Link hidden: Login to view to search for your state website.
Select the website for your local state government.
Then go to the business section and search for reseller tax ID (note you may need to try a few variations as the name varies a bit between states). Often the appropriate forms you need to fill in will be online, or there will at least be a contact.
As for cost, this will vary from state to state.
Hope that helps :D