E1 card oscillator replace, timing accuracy problem

Hi Guys, I am working with Nokia InSite and MetroSite units and now it is obvious, that I have a timing accuracy problem with my E1 dahdi card. According to "dahdi_test" I have a magnitude worse accuracy compared to the GSM specs. I can measure 99.995% accuracy compared to the required 99.99975%. MY question is what can I do about it? My first idea was to replace the oscillator on the card, which by default has a 20ppm oscillator on it. I was able to find some 10ppm oscillators but they are not matching the required frequency (8.192MHz). It would be nice to hear some ideas about how can I solve this issue. Thanks! BR, Csaba