New package trays appear to go for $40 to $100, possibly cheaper on eBay. It's not a lot, but you can easily build one yourself for less. This is how I built mine.

Step 1
Remove the old package tray, if you have one. If you don't, then it'll take more work to fit your new piece in unless you can find a template to use. Start by taking out the back of the rear seat then the plastic trim above it on either side. If you leave the trim in place, it makes it harder to pull the old tray out and...