Realistically, I'm not aware of anyone who could come in off the street and make an immediate, significant difference. I agree with most if the posters here that they won't trade any draft capital either.
Like it or not, there are backup players on this team. They are paid for this exact scenario. They made an NFL roster so they must have some level of talent.
At this point, we'll have to see what OLeary is capable of. Logan Thomas hasn't been used much. I know next to nothing about Lee, so I'm not going to sit here and tell you he sucks.
Its a temporary problem, and this is how teams deal with temporary problems.