It says "Press here to hear theme": http://www.pcperspectives.com/hillbillies/
but it's the one at the *end* of the show, not the beginning.

There seems to be a CD:

        
The Beverly Hillbillies
by Original Soundtrack
Format:         Compact Disc - see all formats
Released:         09/28/1993
Label:         Fox
UPC:         078636631325

I found it on mysimon.com