I don't know if anyone makes them. What I do in such a case is run a CAT5 (because I always have it on hand) from near the RF unit to near the projector, then cut the wire on the IR emitter, cutting about a foot from the plug.

The two wires of the emitter must be connected back together the same way, but these wires will have one wire looking like silver, the other like brass; or there will be a stripe running the length of the wire... or some other such thing.

Let's say you've got silver and brass colors. Take the silver and connect it to the blue wire of the CAT5 that has a minor white stripe. Do the same thing at the other end. Then take the brass and connect it to the white wire with a blue stripe, and do the same at the other end.

It does not matter at all what goes where, as long as they are the same at both ends.