If your motherboard has an available PCI slot open, your best bet may be to find an older (used) Soundblaster Live! or other (hardware based) soundcard with built-in gameport and install it into your machine.
Don't try to use an off brand or built-in motherboard port as the chipsets on these often don't support full gameport funtionality.
Make sure you also go into your motherboard's BIOS and disable any on-board soundcard and game/midi port settings to avoid conflicts with the new hardware.
However, if I recall correctly, Microsoft removed full (2-way) functionality from the gameport with the release of WinXP, claiming that this was a possible route for hackers into your machine, although I never heard of this happening.
Anyway this was the reason I had to switch from my old reliable CH gameport equipment (and Win98) to CH USB based controllers and WinXP.
Good Luck!
CptA