Yeh he shows up in exchange shop later on so it depends on how much you want him. You should have stuck with Boxes if you wanted him, from what i saw he came roughly every 200-500 boxes, but even without him boxes had decent return on coupons from ''junk'' items.

Next best option would be black market, he would be 3200 - 4800 coupons from there since he is 40/60 per frag. Seal scrolls is well, a gamble, you could get him early or you could not get him even after few hundred scrolls.