If you have a drill and a local Harbor Freight, you can get a set of hole saws for ~$6. It's not great, but it does work. I've used a set for several years and curse it every time, but it does the job so I haven't replaced it. If you have ~$30, I bet HD, Lowes, or Sears would be a good place to check out (if you are in the states anyway). Sand paper can fix the hole size, but it will take longer than a dremel/die grinder. Harbor Freight probably sells a knock off dremel for ~$10-15.