He came once in sakura gift where there was an option to buy him with coupons. His initial introduction was in a new event,(dont remember the name, but was based on draws for which you pay in coupons), but it was too much RNG and you just get 1 frag at a time if you are lucky in a draw. He was also there in lucky * which is again RNG. But basically you could have got a lot of his frags for free from time limited shop( has been recurring for a long time now with that explosive gift pack), and get him by sweeps, and as you are a spender you could get him by points you get on spending ingots...I got around 35 frags from all previous events(i didnt spend as such for him, but had to spend for rebates and grabbed his frags whenever i can). They have been giving his frags out too easily for his practical destruction capabilities.

The other 40 fragments, anyways, would cost around 10-11k coupons.

He was available in mission general mobilization event 2 or 3 cycles ago if I'm not mistaken. Don't worry, he should appear soon in a normal, coupon-available way.