Go buy a priests shirt and collar.
Now go to a toy store (like a Toys R Us, something big) and head to the doll section.Find the biggest male doll you can find. Life size would be good, bigger would be even better for the exagerated feel. If you can't find life size you may have to go to someplace like Michaels and buy just a head and then go to KMart or something and buy a shirt and a pair of boys pants and stuff them.
Now, sew the doll (or the clothes) with the face inward to the crotch on a pair of black pants. Put on the preachers collar and shirt. Voiala, offensive hilarious costume.