A Rolleinar 3 gets you pretty close already. If you have
an f/2.8 Rolleiflex that takes Bay III accessories, you
can get a 0.70x Tele Rolleinar, and stack a Rolleinar 3
on top of it easy. The Tele Rolleinars are one-piece
goggles that fit over both lenses, with Bay III mounts
for both lenses so fitting conventional Rolleinars on
top works. The Tele Rolleinars are a bit pricey but
I like leaving one on my 2.8E as a way of getting a
step closer to my subject.