Not real expensive, but it should be simple enough to make up one.
Personally, if I wanted to make one from plans, I'd start at the local library, and see what they've got. But, if I couldn't find a book there with plans in it, I'd find the name of a book that does have plans, and then have the library special order it. You have to give the book back, but the price is a lot less than buying the book.
JOAT Yes, it's my truck. No, I won''t help you move. - Seen on a bumper sticker