I'm pretty surprised they both broke! I've gone years of harsh use without damaging a seal. I'll echo Kaihp in saying you should check for some sort of cause.
I've heard that Canon's sometimes replaced them for free, even out of warranty, but I'm not 100% sure on that. Should be a cheap fix though, it's an non-invasive repair that will take maybe 10 minutes and the part costs maybe $3. Of course to get it done by a professional it will cost more, but you can actually replace them on your own if you feel confident about it.