Contact lenses for cosplay

Contents

Why?

Because your character is badass and has red/gold/green eyes, and your eyes are neither red nor gold nor green

Visit your optometrist, they need to check that contacts are suitable for your eyes (ie. won't make you blind for some reason). This is largely a formality.
The optometrist produces a prescription. This roughly says that you're okay to get contacts, and also how messed up your eyes are if you're myopic/hyperopic/astigmatic
Get a copy of the prescription from your optometrist
Most people get contacts from their optometrist, that's not a bad time to ask about proper care and usage of lenses, maybe ask for a trial pack of something
Now that you've got the prescription, you're also free to get your lenses from wherever else too

The optometrist visit is covered by medicare
- It presumably has a nominal dollar-value, but you can't get it by paying for it, it's just covered
Getting contacts online is usually cheaper, but there's roughly a 4x incidence of infection in people who do
- Citation needed for the 4x figure
- This doesn't say anything about the absolute risk of infection (ie. 1-in-4million to 1-in-1million is kinda no big deal)
- This infection risk is mostly due to poor hygiene and not having been instructed properly