The question people in Australia often ask is - where can they buy a Breathalyzer in Melbourne?
The answer is quite simple really - buy it online.
While there will be physical stores which sell breathalyzers, they are hard to find and will most likely have a limited range of products to select form.
So, the much better option is to look Online, obviously we are biased towards breathalyzersonline.com.au, but a Google Search for breathalyzers online will bring up a few different online stores.
When you order online you will normally receive your breathalyser in 1-2 days.
When you are deciding which one is the best value for you - make sure you take Postage into consideration, as some sites offer Free Shipping, while other charge that as an extra, so you should calculate the total cost to yourself.
You should also have a look at their Comparison Charts, so you can see which one is the best to suit your needs.