You need a Rolleinar 1 set to get a bit closer. Most Rollei 2.8 TLR's
use Bay 3 size lens attachments.
You'll find oodles of these sets on Ebay.
80mm on 6X6 is quite short for portraits and some Rollei TLR users
shoot 35mm film in their cameras using the 35mm Rolleikin adapter for
this.
You might watch for a 1.5 Zeiss Mutar which is an auxilliary tele lens
assembly but is generally priced at about $600 used.
Wonderful camera, enjoy!