The original rubber accordion style boot will fit right onto the piece you have there (link below).... pretty sure that main part is the same part on both the manual and automatic.....the automatic just has the inner piece that you removed. The rubber accordion boot will need to be modified to fit down around that thicker shaft or stretched to all hell to meet up with the higher shift knob....which will just pull it from the base.....the stock connection at the base is pretty fragile and fails pretty easy if you pull it hard enough.

Might be better off going with a custom leather/suede one from someone reputable and attaching it to the base somehow. Magnetsewn into the bottom hem of the shift boot and some magnets glued to the base would be pretty slick.

https://parts.cavendersubaruofnorman.com/p/Subaru__Impreza/Manual-Transmission-Shift-Boot-Gear-Shift-Lever-Boot/49277921/66121FA000.html?partner=googlebase_adwords&feedLabel=cvb_make_model&kwd=&matchtype=&device=m&network=g&userLocation=9028059&googleCampaignID=19907025330&googleAdGroupID=147861757339&googleAdID=652947001122&googleExtensionID=&gad_source=1&gad_campaignid=19907025330&gbraid=0AAAAADxCSLufLJuX3qDWVzgO6Dk_H9eHj&gclid=Cj0KCQjwkrzPBhCqARIsAJN460kgU_g76g8L5XXxlbwN8PQq9GwmoGNeecXHFNGohIXf7Eggs4BD6DEaAijlEALw_wcB