I think the IR extender just uses a 3.5mm mono connector. So my guess would be that a 3.5mm mono Y splitter would work.

https://www.amazon.com/3-5mm-Mono-Y-adapter-Cable-Male/dp/B00I01X9P4/

There are IR transmitters in the shell of the 2nd gen, in case you can get it within line of sight of your equipment.