I used the 2007 Guide to Literary Agents (Published by Writers Digest, I believe). The listings have designations for type of product they handle. The listing are sorted in the back of the book by genre. I only found about 20 agents and didn't consider them all credible. (I posted on this a couple of weeks ago...you can go back and look for it.)
My book is historical fiction -- imaginary characters set against the real events of the first century. It's not strongly religious, nobody gets saved or experiences the miraculous. It does, however, have a very reverent retelling of the crucifixion. My wife keeps telling me to query mainline agents, but I'm afraid they're just not going to "get" the book. (The Christmas story is told through the eyes of an 8-year-old girl.)
I don't know anything about your book, but one agent not listed for Christian writers was Judith Riven at Judith Riven Literary Agency. She agents Eva Etzioni-Halevy's books. They're really romances in an old testament setting.
I'd be interested in hearing about anyone you turn up. I can probably give you a few more names if you need them. Let me know.