Most hardware stores have an assortment of springs. I'm sure you can find one to get you by.
That's what I thought, too. Spent over an hour at Granger with a 2" thick book of springs. Nothing even close that'll work for any length of time. I've actually welded the little bastard now, but I'm not sure how long it's gonna last so I'm still looking. All my usual suppliers are at Davenport for the weekend. :-(Most hardware stores have an assortment of springs. I'm sure you can find one to get you by.