welcome to the boards rick...
I'm a fellow Dodgers collector and have come across quite a few Target sets over the years. I've kept two for myself, one sealed set and one that I opened to separate (the cards are perforated for those who don't know) and enjoy looking at. In fact, once I mailed an extra set I had to Vin Scully as a gift along with a 1982 Volpe of Vin requesting his autograph. My gift offering must have worked because Vin returned the Volpe signed! Oh, I should add, he chose to return the Target set back to me, lol. Who needs cards when it's all in
To answer your question, when I need random singles to complete my team sets at a reasonable price I usually buy from burbank sportscards on beckett marketplace. In addition, these two sites have assisted me a little over the years:
http://www.sportlots.com/
http://www.comc.com/