I'm not aware of any way to turn them directly to cash. You can, however, turn them indirectly to cash through play.
I did this by playing the 70FPP x 10 SNG's. When I won, I got a buyin to an $11 MTT. I then unregistered and had 11 T$ (tournament dollars) put in my account.
The T$ can then be used to enter any cash tournament. My preference was the $5.5 x 9 SNGs since they are the simplest for me. Whenever I cashed in those SNGs, that was real cash.
All that being said, it sounds like you've had a bad run at the tables so this might not work for you either. It would, however, give you another chance to fix your game without another investment.