New white toilets are really very inexpensive. An entire unit can be had with all the trimmings for less than $150, and if you're careful, you can find them on clearance from time to time, for really cheap!
You might try downloading copernic (http://www.copernic.com) and searching for "toilet seat", but I don't know how much luck you'd find.
Make a new post at the top of the board where people will find it, and specify how far apart the mounting holes are, the width diameter and the length diameter of the bowl opening (most toilets have an oval shape). That will help people identify what you are looking for, but again, I don't know how much success you'd have here.