Thanks to Buzzonion I can confirm the below 4th gen part fits the 5th gen:
Rear LCA inner bush - 52354-SS0-023
£21.25
Is a direct replacement for the 5th gen rear lower arm camber adjuster bush.
Honda cannot supply the 5th gen lower arm camber bush separately, they sell the lower arm and the bush as one unit for £220. No motor factor can supply a suitable replacement bush either. By ripping out the old bush and using the above 4g part you save over £200 per side. Honda themselves are not aware of this compatability.