Kevin,
The 'O' rings supplied by the LDMCC would have been to an imperial size with a 1" bore - have a look at Simply Bearings website, there may be a metric 'O' ring with a 25mm bore that is slightly larger in section. Fitting the larger section ring into the end fittings shouldn't be a problem, as 'O' ring grooves are usually wide enough to allow the ring to float.
Regards,
Eddie.