Not sure if you're handy or know someone who is, but I saw a great idea the other day and am going to try it this winter. I need nice garden benches too.

The idea is to make one out of the headboard and baseboard of a twin size bed. You can get these at flea markets/yard sales/second hand stores/etc.

The headboard becomes the back of the bench. The baseboard, after being cut in half right in the middle becomes the sides of the bench, and then a couple of planks are placed across for the seating. If the side boards of the bed are available, those can be used for the seating.

I think they are very unique! Here's a link to a posting of such at the Garden Junk Forum.

Here is a link that might be useful: Garden Benches from beds.