Most welcome Colrose

Before it gets too much use, check/change the gearhead oil as thats a pricey $300 assembly now

Penrite transoil sae140 1l bottle might be easier to procure. 1l is about $20 delivered https://automotivesuperstore.com.au/penrite-t140001?

The other option that is easier again is penrite semifluid steering box grease https://www.repco.com.au/en/oils-fl...ease-450g-cartridge-semi00045/p/A9372070

Really, so long as it has a high viscosity lubricant (that critically does not have sulfur in it) the gearbox will last a very long time.

503335 is only available through a masport dealer, Rewells mower service in castlemaine is apparently your closest.