Australian Maher, 46, was renowned for his toughness as a strong-running second-row with the East Yorkshire club between 2000 and 2003.
He made 100 appearances for Hull, scoring 25 tries, having initially moved to the UK with Rochdale Hornets in 1998 before joining Gateshead Thunder the following year.
Greenhill, the former Australia second-row who played alongside Maher for FC in 2002 and 2003 before joining Castleford Tigers, is searching for pictures and action of his friend for the fundraiser at Wynnum Manly Seagulls on February 22.
MND is an uncommon but fatal debilitating condition that affects the brain and nervous system.
South Sydney and England star Sam Burgess’ father Mark - the former Hunslet and Dewsbury prop - died from the disease at the age of 45 while ex-Scotland lock Doddie Weir, 48, and former Bradford City captain Stephen Darby, 30, are both currently fighting the condition.
The Yorkshire Post has sent these three images of Maher but anyone who can provide anymore should get in touch with the Hull FC Ex-Players Association via Facebook or contact Hull FC on 01482 337 520.