Rum extract might do the trick. Try using a tbl or so, taste as you go. I would not omit the rum altogether, as it imparts a certain flavor to the dish. Here's a link to give you some ideas (and a lovely recipe too, I might add, IMO.)
I sometimes add a cup or so, of fresh brewed coffee to recipes, roasts etc. That is one idea; but I don't know how the flavors will 'marry' in this particular dish. Also depends on your taste. Beef broth in place of chicken broth, might be another way to go.