You can use Silicone RTV kitchen and bath caulk or, There is a new putty on the block that can be used...
Sta Put® Ultra™
A unique, professional grade non staining plumber’s putty that is safe for most types of plumbing fixtures and surfaces. Unlike all other plumber’s putty Sta Put Ultra is oil-free and can be used without pre-treatment. This includes natural, porous surfaces such as stone, marble, granite, plastics, rubber, and fiberglass, as well as grout and on manufactured sinks, shower bases, countertops, and other surfaces. Molds easily, remains permanently soft, malleable, and flexible. Sta Put Ultra does not melt, rot, crumble, dry out, or shrink. Easy to clean-up. Does not leave a greasy residue on hands or surfaces. Meets or exceeds Federal Specification A-A-3110 (formerly TT-P-1536A).
U.S. and foreign patents pending.