I have no idea about the size. I know that IPD sells a magnetic one for $8(www.ipdusa.com) and a dealer should carry a few also. Most car parts stores carry universal replacement drain plugs.

Here is a trick I have used before to find a bolt. Cut a 3 inch piece out of a wooden ruler. Then trim the sides so that it tapers from slightly smaller than the hole to slightly larger than the hole. you can then put the wood into the hole and screw it into the hole. the threads on the oil pan will cut and crush the wood to match the bolt. take it to the hardware store and match it up.