Join the the RDF (when the recruiting embargo ends that is).
Arktis only made kit for the ARW and limited issue/proof of concept trials so it was a small production run.
A few years ago they advertised Irish camo. jackets and trousers on their US website but I have not seen them since.
You could try phoning them directly to see if they have anything left or if that doesn't work ask one of the surplus traders near them to make discrete enquiries on your behalf, ie Endicotts.
Markruss Stores of Bristol sell a lot of Arktis produced gear cheaply which I think they buy directly from the factory as production overruns. Again try calling them.
http://www.yell.com/b/Marcruss+Stor...Equipment-Bristol-BS84RY-900152324/index.html
You could also try asking a serving (or ex.)PDF or RDF member to sell kit, there is always buckshee gear around or maybe a lad is stuck for cash or emigrating to Oz.
A warning though, wearing items of the Irish Army uniform (and Garda issue gear for that matter) without due cause to do so is an offence .
I've always wondered if dyeing French camo. (Central Europe, CE) a light shade of green would produce the same result Irish camo.
Happy trails...torc.