The 922-4201 adapter is probably the VGA (male HD15)->Mac video (female DB15) adapter that did ship with the blue G3s, and all the PowerBooks with VGA outputs (at least until the Pismo, inclusive).
Regardless of whoever told you that it's a PowerBook accessory -- that may be true, but assuming it is the part above, it is the right adapter and should work fine.
Similar adapters (by "similar", I mean electrically identical, differing only in the color of the plastic) shipped with various PowerBooks, Power Macs, Apple displays, and Mac graphics cards. Any one of them should work equally well.
tooki