Hmm, guess I was right when I thought this was too obscure a thing to want to do
I've decided to gamble and have invested in four of these USB game ports - less than £20 ($40) on eBay from Germany so I figured it was worth the gamble. My concern is that the machine will only see one of them ... but I'll post here again and confirm whether it works on the offchance that someone is searching these forums for just this information in the future.