I had the same problem with my Momo shifter.
My shifter has a ring at the bottom that unscrews, so I cut the ziptie that holds the plastic trim ring on the stock boot.
Then unsrewed the shifter ring and push the tip of the boot through the ring.
Then you can ziptie it or glue it to top of the shaft just below the shifter, and screw the trim ring back in place your done.
I would try this first if you dont like the way it looks, try the other method that fastcat99 pointed out.