I thought Donorcycle was the common term. At least as a paramedic for nearly 25 years it's the one I heard the most.
DonH Midwest Me 56 WAW-EXW 55 Met 11/95 / Married 5/00 Bomb 6/20/05 / She Filed on 6/2/06 / Divorced on 10/9/06 4 who'd qualify as GF since D & dated about 25 women since D