Very nice work!! I'm just about to change my automatic gear knob too. Would you tell me what size do i have to look for, or all the knobs should fit?
I think most aftermarket knobs come with a couple of plastic sleeves that you put in the knob and over the stick ...
I bought mine through ebay, it came from the UK. So have a look at a few and you'll see the sleeves... they come with a few grub screws and allen key to fit it.
I actually fitted it. Making sure the grub screws made a mark on the plastic sleeve, then removed it.. and drilled holes through the sleeve where the grub screws made the marks... got longer grub screws so the lock onto the gearstick shaft.... much more stable fitment...
Takes time but I prefer it this way.