Earbud replacement tips

Need some replacement if my Sennheiser CX 175 tips ever get lost. Bought these: http://www.ebay.com.au/itm/131501006112?_trksid=p2050601.m570.l4467&_trkparms=gh1g%3DI131501006112.N19.S2.M-4984.R1.TR1 but when I put them onto the earpods they took a bit of struggle to fit them on. Oh also preferably the ones that have near total isolation from the enviroment.