Well, I knew I'd hit a snag sooner or later. Things can't go perfectly all the time, can they? It looks like I'll have to use the in-house artwork after all. The publisher needs the finished piece by the end of September and wants to retain copyright on the finished art, and it doesn't make sense from the artist's standpoint to take a measely few hundred bucks to do a painting he/she cannot sell prints of or otherwise display for his/her own promotion purposes. An artist willing to relinquish copyright is going to want a heckuvalot more money for it than what I can afford.
I can't say I'm not disappointed. The artist I'd chosen is very talented. Take a look at her online gallery at www.ldiehl.com and I'm sure you'll agree. Maybe my next book.