Have you considered using a die grinder or a rat tail file to move the inboard ends of the slots closer together? Just because somebody else decided how close the slots are doesn't mean you have to take their idea as gospel.
I took a look at that puller and lengthening the slots is a no-go as there's a thrust bearing that's nearly that large in diameter. The slots would have to go in to the space where the bearing is. I'll go with a rental puller for those gears.
