Hello, i hope i dont come off as too brutally honest that it may seem offensive, but the only way you can do that, (something which i practise)
is to instead of turning them away, offer to draw something up for them. and the only way they will like it is that if its better then the original.
take the time to listen to what they want. offer solutions. its not an easy road, i do 99% custom work. i spend too much time drawing. at least 16 hours per design.