Doing a quick search on Ebay and reading some manuals seems like I can get a decent level sensor for $150 - $25 on Ebay. Think I'm going to pull the trigger on this one:
Made by flow line, it measures between 2" - 48" with a 3 mm accuracy. Should be good enough. Manual is here if any one is interested.
http://www.flowline.com/pdf/disconti...u12-lu13-m.pdf