To program a token onto an existing Coin Mechanism, the token would need to be metal.
You will need to have the cooperation of your vending machine supplier who either via there supplier or directly have to reprogram the coin mechanism.
20 or more metal tokens will be required to test the mechanism. The firm reprograming will need to know what machine it goes into (Make/Model) and the Coin Acceptor Module (Make/Model). Assuming that the Acceptor is compatable the cost is around €65.
The other option is to go Cashless.
If you have no vending service firm I can recommend a company in Ireland that deals either directly or via partners with the majority of vending sites in Ireland.