I have home-made white cards and purchased gray cards. When white balance or exposure needs tweeking, that is handy enough.  At work, where I am the "resident" product photographer(because I have the camera and macro lens) with no real lighting set-up, I simply do  a custom white balance and alter if need be.  That is simple enough for me and easy enough at mimimal expense.  If I can't get decent white balance then I shoot in raw.      My 1 cent worth.    TomDart.