What about the stain "eraser" for kitchens & bathrooms - is it by Mr. Clean? I haven't bought one or I'd know but someone brought one to the office. It looks like a white sponge or markerboard eraser, and it's done wonders around here on white doors, trim, things like that. Maybe it'd do the saddle, too.

For white bar tape, my shop recommends Armour-All Cleaning wipes. I don't know how that translates to saddles...