If you know someone who is in Thailand , Vietnam , malayasia , Indonesia even china then parts won't be an issue and will be cheaper. Aamayama and ebay would be last options due to the tax.
Genuine parts are same price as toyotas and other brands. Sometimes cheaper when you compare the agent prices.
But ordinary part shops in your town won't carry them.
If you are getting a Mazda I recommend only demios or Mazda 3s because they have plenty of parts and even normal shops carry them. Mazda 6 its bit difficult to find . Same thing like a Corolla and a Camry.
But a good looking and a sporty car.
Engine parts won't be an issue , body party will be the issue if you meet with an accident.