Loooong time since I chased these down, but I am pretty sure you can get them for free, linux or windows servers. google for 'Open Source' or 'free' ecommerce scripts.
Most have some content management as well.
When you find one you like, get a host and upload the scripts.
Biggest issue is the merchant bank connection.
IIRC, paypal may even have links to some, with the banking set up to run via paypal.
Edit: Getting one written from the ground up can cost around the 50k mark! Someone I know paid that.