You have to stay within editons. B5 Passats sunshades will fit any B5 Passat. The sunshade from a MkIV Jetta GLX will fit any MkIV Jetta. A Passat rear deck WILL NOT fit a Jetta.
I have a tan Jetta decklid/sunshade for sale in the classifieds. If you need black/grey, I'm sure it could be recovered in black quite cheaply.