You will need the mesh from MESH_ju-beos_bellbottoms050905 for these pants to show up in your game.
Here are 8 pairs of flared/bell bottom jeans for the bodybuilder mesh.
They are organised into 2 rar files with 4 pairs of jeans in each.
Credit goes to Marvine and Beosboxboy for the mesh and to Maxis for the textures.