Admire can be used over the top, but you can not do that after having treated the seed with Admire. The $600 a gallon price can be a tad much for a small patch. 

CPB gets resistant to any one chemical very quickly. Make sure you only do two or three doses of one chemical a week apart before switching to a different chemistry.

A couple years ago once I rotated through my usual chemicals and still had problems I got some Colorado Potato Beetle Beater which is organic Spinosad.  It actually works quite well if you follow through and respray a week later, even if you don't see any beetles.  Comes in a homeowner convenient size.