This is what we've found are the requirements for the Category 'A' stamp, but these things can change so it's worth doing some of your own research too.
To get a 'Category A' permit in the US, you need a valid US motorcycle permit. A regular drivers license will only enable you to get a type B permit. You can get an international drivers permit at a AAA office.
You may need to have a Class 6 Endorsement (motorcycles) on your driving license to ensure you get the Category A stamped. Check the AA website for the most recent updates.
Australia now has a standard across all states. To get Category A stamped in you IDP you will need a motorcycle licence (R or RE class). Check with your local authorities to ensure this is the case.
You have three choices for getting the IDP: NAF (Norges Automobilforbund), KNA (Kongelig Norsk Automobilklub) or MA (Motorførernes Avholdsforbund). You also need to hold a valid Class A drivers license.
If your country is not listed above, we have not managed to collate information from previous teams in those countries. Please do e-mail in to firstname.lastname@example.org