Based on your description it sounds like you're looking for what's called a "sensor loupe".I am looking for a tool to clean the sensor, I have seen one that fit's to where the lens connects and has a light and holes in the side to allow acces to the sensor, I cannot remberber the name of this item, anybody seen them?
I would buy from the dealer, this was just a quick search while at work.thanks Scott, that is the one I had seen sometime ago and could not remember the name of it, only one prob with the ebay item seller only has a 96% rating.