SEO URL with just lowest level category and product name

I would like to clean up and shorten my URLs but maintain the same category hierarchy on my site. Is there a way to change the SEO URL to only show the lowest level category for a given product instead of using all the parent categories?
For example:
http://www.airstreamsupply.com/New-Airs ... key-680050
would become:
http://www.airstreamsupply.com/Key-Blan ... key-680050

I am using opencart version 1.5.6.4