Cheapest and fastest option would be to rebarrel it to a 22 magnum (WMR). Ammo is relatively available and relatively cheap. Or .17 HMR.
Next best thing would be to contact James Calhoon in the States (Google him) and buy a set of his prints for converting the bolt to centerfire. There is one wildcat option that may allow you to use your barrel as-is, using a necked 22 mag centerfire case (22 CCM, IIRC, good luck with finding cases!) and reload with available .204 bullets. Otherwise, lots of guys have built .22 Hornets, or .17Ackley Hornets out of them. May be able to salvage the barrel blank, but it should be threaded onto the action to be safe for the higher pressures of the CF loads.
Either way, it's gonna cost ya a bit. Hope you got it cheap!
Maybe we'll see some Aquila ammo up here, but then, maybe never. Check out the stickies in the Ammo forum. One has a link to the list of approved-for-import ammo that is allowed into the country. Chances of anyone seeing the 5mm rimfire as a major source of long term profit margin seem slim. I would not hold my breath.
Cheers
Trev