How to produce a certain amount of volts and amps?
Considering "power supplies" are generally referring to constant-voltage variable-current supplies, the current your device is referring to isn't what it needs to dump all the time guaranteed - it just means the maximum. 

The same goes for when you find a power supply, e.g. one that says "24V 5A Power Supply". It doesn't dump 5A into a load all the time (although that does exist, a constant-current variable-voltage power supply, I've made a 240W one for a Peltier control system), it just means that this "voltage source", if you will, can supply 0-5A depending on the load.

So, you just need to find one that can support up to 2A. One that says 3A, 4A, 5A, etc. will be just as suitable.

Don't worry - a lot of people don't realise this. I'm an electronics engineer now, but only 8 years ago I was confused reading cigarette car charges - "How does this thing supply 5V AND 1A at the same time? Doesn't the current depend on the voltage?" was a question I always thought to myself, until I got my degree.

As for how to actually go about this - you say you have batteries. These probably won't be suitable, except maybe 2 x 9V batteries in series. Best to do would be to use a power-point outlet, with a proper wall wart power supply. Here is one on Ebay that is within the voltage you need: https://www.ebay.com.au/itm/Plug-In-Switch-Mode-18V-2A-DC-Regulated-Power-Supply-ErP-Comp-36W-UK-Wall-Wart/322761626532?hash=item4b261793a4:g:t9IAAOSwP4ZZwYy~

That one isn't very cheap, so I would shop around.