I've fitted a BMW ZHP one to all of my Z4s as it's weightier and a bit shorter than the OE part.
Here's a link to the genuine one with the BMW Part Number. https://www.ebay.co.uk/itm/113876388362?fits=Car+Make%3ABMW&_skw=bmw+zhp+gear+knob&epid=6033704112&itmmeta=01JT956STWX7KSCXNDVJHF43PW&hash=item1a838fca
If your car is a 5 speed it's the same Part Number but the last 3 digits are "031" instead of "886".
Don't be tempted by cheap ones on aliexpress or similar as they aren't weighted!