The $69.95 one looks like your best bet. I bought one from www.denniskirk.com this year for $75.00. It is a PARTS UNLIMITED brand, and it's just as good as any factory cover. They make them custom fit per your machine, and they ship emediatly!
On the Dennis Kirk web page in the upper right hand corner is a box for part#. I think part number 56850 is the one for your sled. Type in the number and hit the go button. When it comes up you can click the (See what sleds this fits) line. Yours is listed. If you have a 580 sks-pt the part number is 56829.