To get an ashtray for the dash, you're gonna need a whole new center stack cover (the big black cover in the middle). The 98's have 3 switches then the ashtray. The door is only one part. The back part is part of that stack. I know this cuz I cut it off putting in a second bezel.
Try a wrecking yard for a wrecked TJ and see if that center cover is still in one of em and you could probably get it dirt cheap.
I doubt you'll find many willing to part with their entire cover.
You can see it here, being cut off.
Sorry it is so big - not my pic.