Uhm, what do you mean by give credit? is it just like "hey this xxxnamed user made this for us" or are you going to pay with money?
The only users I saw who has done sigs for free are mostly the ppl who are just starting, since they have to build up some trust. They're mostly on Services board.
Now if you do have money to pay for it, that makes things easier! Just go through this list of
Overview of Bitcointalk Designers, pick an artist who does sigs, check their works, fees etc.. and if you're fine with it, contact them.
