What can I use to break down a stone in the GB ?

I have tried to get Gold Coin Grass but we dont have any here, what else can I use to break down my 2cm stone in my GB. I have done 4 flushes already following H.Clarke's method with good results. Could a stone that size pass through my GB just by using H.Clarke method? I'm planning on another flush today, having slight heartburn. I will be traveling on Thursday and hope my 5th flush would help me feel better or should I wait until I return and then do my 5th flush?? decision, decision !!