I got one for my A900, but it cannot be used with eyepiece correction lenses. Now I use a third party angle finder which almost fits, but not quite! There is just enough gap to accommodate the correction lens and it's usable!
Of course, you don't need correction lenses with the angle finder (it has dioptre adjustment built in), but I really don't want to be handling something as small and fiddly as a correction lens at a difficult location (e.g, boggy Scottish moorland with heather underfoot). Eventually I would be sure to drop it and never find it again.