Lol you are going too far back. From the long shaft with the flying Rippers in Brinstar that you use as steps later, go right into the water room, then right one more screen. If you have the Hi-Jump Boots(or you are damn good at Turbo Bombing), then the minute you enter the second water filled room with the Snappers, shoot up and the block will open up. Jump up there and the Spazer is right there. ^^

Hope that helps. I know you said you were in Norfair, but i cannot recall a time i was actually stuck in Norfair itself, however i do remember being stumped all those years back at the lower half of Brinstar.