You can get genuine ones here. A little on the pricey side though.
Venting the silicon tips of E-Q7.
It looks like that E-Q5 has some reputation in terms of sound over E-Q7 and it is said that Q5 has somewhat less bass in amount than Q7 but better treble in quality... Considering both models, I think the major difference is that Q7's body is completely shielded while Q5 has some space to vent at its rear cable holes. Q5's hole may not be designed to have intentional acoustic effects, but I think the said difference of Q7 and Q5's sound signatures is consistent to the effects of venting the phones.
In general I like the sound of Q7, it has very well balanced frequency response and high resolution. The weakest point of Q7 is its a bit grainy treble I think. I like cool and objective sound, but Q7 might lack some sweetness of treble necessary to present violins or female voices. So I thought venting Q7 can be worth to try. I made a tiny hole in the inner cylinder of the silicon tip with a needle. The result is as I supposed, smoother and sweeter high but less definite and reduced bass. I've listened to it for about a day. It looks promising but I have to listen for a longer time comparing it to the original. I'm not sure the resulting sound signature is ideal or well balanced, but I think it is worth to try and want to hear opinions from others. (Maybe somewhere in the forum others have tried similar things, if so would you locate it?)
Of course you will need spare silicon tips, I've got from the local distributor in my country for about $4/pair.