discount codes and simple paypal shopping cart

I recently launched a site for a client that includes the WordPress Simple Paypal Shopping Cart plug-in. He is guest blogging at another website now, and would like to offer a discount to the readers of that blog. I figure the best way to do this would be to give the readers on the other blog a discount code, but there’s no way to do that with this plug-in. I figure the options are

(a) hire someone to modify the plug-in, or

(b) use a different plug-in…which could mean a fair amount of effort to redo all of his product pages. Although the latter has an advantage in that it would be easier to add products to the site if his current products were in a separate database, not just listed on a couple of pages with short codes, which was the simplest solution at the time the site was designed.

Also wondering if it’s possible to leave the site as is and enable the discount through paypal (although a search of these forums turned up a discussion that indicated this is not possible).

Any recommendations on a plug-in, or an alternate solution?