I had a post on this here: https://www.reddit.com/r/Wrangler/comments/qbykwy/using_stock_shift_knob_on_bm_shifter/
And a link to the part: https://www.amazon.com/gp/product/B095XCFSLT/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1