Etymotic ER4 P to S adapter

I’m looking to get and adapter for my Etymotic ER4P to make them behave like the ER4S. Can I just use a regular old impedance adapter or is the one Etymotic sells doing something else besides adding resistance? If so what ohms should I be looking for to match the official adapter?

Secondly, if I can just use a regular impedance adapter does one like this exist, where it’s 1/4" to 3.5mm and just a tip, not a dongle style? I hate dongles.