Ah yes, just been to contact details and it's Canadian :( bummer!
Why don't you buy another chunky yarn instead? Shetland chunky is 25% wool, the rest iirc is acrylic and nylon (used to be in the trade). I don't know id Sirdar still make Country Style chunky, but that was always quite a favourable alternative (15% wool). Otherwise, I'd just simply find a chunky that you like that has at least 15% wool in it and use that. Check your tension first and buy an extra ball just in case (well, that's what I always did/do).