I went through a lot of screw piloting drill bits before I settled on this combination. The tapered drill bit is sold by Lee Valley, and the countersink is a Dimar.  It has carbide cutters and is made of two parts which clamp around the drill bit allowing it to be installed on any drill bit up to 1/4" diameter.

It is more expensive that some others, but lasts for years and years.  And it works!  Money well spent.