There are alternatives if you're happily working outside the land of bureaucratic BS.
If you are a bit handy with a soldering iron it's fairly easy to put yourself together a power supply that is capable of 3A.. you can get little switch mode power supply modules off ebay which are based on a popular Texas Instruments chipset (LM2596). They only cost about £3.
I have used these many times with success...
However, it helps also to add a little extra filtering in the form of inductance and capacitance, but this is easy to do. (actually on mine I've only added a little extra capacitance and it's been fine)
In the majority of cases the interference is conducted switching noise going back up the 12V aircraft supply, which is then fed into your radio. What happens is that the power supply has a switch inside which is turned on and off very quickly.. the advantage of this is that the voltage is converted down to 5V without wasting power.. the disadvantage is that this on/off switching can create disturbance of the voltages if not properly dealt with - which leads to interference.
This can be sorted by filtering the 12V input to the little power supply to stop it injecting noise into your aircraft 12V (i.e. adding capacitance and a series choke inductor) - just like you would do with a suppressor in car ignition systems. This helps prevent the noise from then getting into the radio from its' power supply.
These little units will happily run at about 80-90% efficiency, so when supplying 2A to the PAW they won't get too hot:
http://www.ebay.co.uk/itm/DC-4V-38V-to-1-25V-36V-5A-Step-Down-Power-Supply-Regulator-24V-12V-9V-5V-UK-/121981769588?hash=item1c66ae1774:g:f54AAOSwo6lWI2DoThe blue potentiometer can be adjusted to ensure you get enough voltage at your device, but you will need to use decent gauge cable as has been mentioned above.
But, only use one of them per device... so don't try to run a PAW AND a tablet off just one of them, it wont work... and don't forget to use an in-line FUSE!
Put it in a small metal box and this will also help get rid of radiated noise (if it's an issue).
Cheers
Andy