All our available nib grades are listed here. We do not have any other grades/feeds available. Our supply of standard medium nibs for the 75 ran out some years ago.
All our nibs are unused, ex-factory stock
If we do not have the nib grade you are seeking, it may be worth trying Lih-Tah Wong at parker75.com or John Mottishaw at nibs.com
Further information on Parker 75 feeds and shells - which feed fits which shell?