InPins are amazing, but there are other perfectly functional options out there. I got mine from a seller on eBay called “cables4pc”. They sell two kinds (maybe more, but these are the most common): a crappy, blue 2-player one, which Kelter Skelter mentioned, and a single, black one which I have and tested (my review is in the converter thread). It cost me like 5 bucks if I recall. Definitely one of the cheapest lag-free options.
I think the main disadvantage is, it doesn’t have LEDs on it like the InPin showing which controller number your stick is assigned to at a glance… but I never needed to use that to be honest. It doesn’t have a Home button on the unit itself but start+select on your stick acts as the Home button.