There are two ways to do this...

1. In the RealTracks picker, there is a column for Simpler Available. If there is an 's' in the appropriate column, Pete's suggestion should work.

2. In the RealTracks picker, click the box to Show RealTracks Variations. The desired instrument may have a Simpler variation - ex: Bass, Acoustic, Bossa EV 085 (A:Simple)