Needed: recomendations for a publisher

Hi there,
I have written a book on the roles of the european churches in the Holocaust. It is in part based on my masters of the same name. It is not a happy story, but one I believe Christians need to know. My professor recomended that I get it published, but I believe that it is Christians, rather than achademics, who need to read it. I have therefore approached Fortress Press, T&T Clark and John Knox Publishers, all of whom rejected it as "not commercial enough." Could anyone recomend other reputable Christian publishing houses for me to try?

Thanks, Colin