I think payment of committee members can get a bit fraught. I could promote bad behaviour as some residents stop treating them as selfless volunteers and start treating them in the same poor manner that they treat the employees of other businesses and/or start making snide suggestions that they are only doing it for the money.
I would recommend instead that someone else, probably another committee member, be lined up to give a nice speech at the AGM describing the exceptional additional work this particular member has done. That person might then propose a motion that the Owners Corporation records it appreciation and authorises the purchase of a gift of a case of the person’s favourite wine or a voucher for a local restaurant or similar.