Take a look at the Olympus FL36 with a Sto-fen Omni bounce. A great combination with the G1. (I use mine on the G1, DLUX4 and E-P2, all with TTL functions.) If you want to use the flip up flash on the G1 for fill, check out Gary Fong's "Puffer". They really soften up the small on camera flash. Good luck.
. . . Burkey