'Love & Hip Hop' -- Taking Over L.A. ... But Can't Land a Star!!!

"Love & Hip Hop" is moving to L.A. for its new spin-off -- with episodes expected to start shooting later this month -- but producers are now facing a HUGE problem ... they can't find a big name to star on it.

Sources close to production tell us, they initially planned to attach Ray J as the headliner, but he's currently tied up hosting "Bad Girls Club All-Stars" on Oxygen so he couldn't sign on.

Now we're told producers are scrambling to find someone else, but it's proving more difficult than they anticipated ... which is somewhat surprising, considering "Love & Hip Hop" is one of VH1's highest-rated shows.

According to sources, producers will start by shooting story lines for the smaller stars who have already signed on, including singer Brooke Valentine, radio DJ Yesi Ortiz, rapper Hazel-E, and video vixen Bria Myles. We're told producers have decided to worry about the bigger stars later.