You could go to www.taobao.com for purchasing the second-time production, but the language is all Chinese.
I am not sure how to get the second-time production in NA but you could keep watching unit-2 and I will keep posting new information about it because RX-79 is also one of my favorite Gundam!
By the way I think the loosing joints problem will not happen again in the unit-2 or 3 if there is 3 coming.