I don't actually do JV's or deal with anything much to do with TV, so I don't really know where the best places would be, sorry.
Have you maybe tried going to sites that deal with TV and asking them for JV's? Most probably you have already done this though.
I done some quick research and found some sites that deal with televisions infomercials
here. Maybe you could ask some of them if they would do a JV with you.
Good luck!