Ferrite cores are usually found on the ends of computer VGA monitor cable, and for the same reasons.

I'm using something like the digikey p/n 240-2143-ND. This is a solid piece that looks something like a ring or tube. With this "solid" type, you need to make sure you have big enough inner diameter to fit the blaster cable's entire connector through it a couple times, looping the the cable through it at least one loop. I wish I could post a picture here....

The better solution might be one of the clamp-on types. These come opened up like a clamshell, and you loop your wire around inside one half of the core, then close & lock the clamshell. You can even bundle a pair of your IR emitter cables into one of these. Model HF70RU10X20X5S is from TDK and is the clamshell type, but it doesn't include the plastic casing - you can easily just tape it together with electrical tape. Their web page is [Link: tdk.co.jp] (see the PDF on the line called: For EMI Suppression / for round cable / Separated Cylindrical).

Just pick one that fits. You might also try your local elect parts store. Remember you need to loop/wind the cable around the ferrite core at least one turn.