Resurrection powder is available to you quite early in the game. At the Monastery when you go upstairs make your way to the water and enter it and follow it back to the waterfall. When you go over the edge of the waterfall you can grab some powder sitting on a rock half-way down (save just before you go over in case you miss) and that should give you at least 3 Resurrections.Also you'll be able to get some more powder in the Upper Monastery in the safe marked 'For Emergency Use Only' and those should get you to Arnika where it is available for sale.