They exist, but can be hard to find cheap, there's also right angle adapters around if it will clear low to the board. Also you don't really need a PCB to make one, if you get a socket with right angle pins, then you can find a junk ISA card with full fingers, saw those off and tag the socket to the tops of them carefully.
Alternatively, there are a few ALS 100+ cards around that are low profile and have the gameport on a ribbon to the bracket that may work. But these have gotten sought after for being pretty good OPL3 copies so prices aren't great.
edit: link for the picture of the ALS 100 card type I was talking about, would consider this overpriced... https://picclick.co.uk/Avance-Logic-Arowana-1 … 3845099219.html
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.