Have you tried diy'ing it? Take the core of the foamie that you can't/won't use with the set that came with the westone's and strip it so the core remains. Then take the core and put the tip you posted above on it. Make sure that it stays on the core itself and then put back on the nozzle itself. Be careful doing this as it may come off in your ear! Other option is to try shure olive tips.
I've been trying the trufit tips that I got on saturday at work today. First off I tried the red long ones, but found whilst they offered excellent isolation they were slightly TOO long for my ear and the monitor itself became a bit uncomfortable. That and the fact the tip seemed to boost the bass a bit too much for my taste. So next at break, I swopped over to the clear black ones and this was more like it except I lost a bit of isolation but not too bad. Not sure whether to stick with this or try the blue ones that came with them. So far so good and well worth the £20 or so it cost. I have read about tips altering the sound before but never actually experienced it like this before!
That's actually a great suggestion. I was just talking about doing that yesterday in fact. We were talking about either gluing or just stretching the silicone over. Have you actually done the DIY before with success? If so, did you glue or just stretch? The reason I ask is that I have melted silicone with glue before, but really don't want the tips coming off in my ears any more.