I don't have this earphone, so take this with a grain of salt, but those look like pretty standard tips. From my experience, a lot of ear-canal phones use pretty similar tips to those, and are basically interchangeable. If you happen to have another set of earphones with the same tips, you could try those on, or if you can find a cheap set you could try those. Other than that, you could try to get replacement tips, such as for the CX300 straight from Sennheiser, since I would imagine those fit as well.
Someone please correct me if I'm wrong.