1) A Black Market can't be ruled out. While they are very careful when it comes to Asterisks and who got access to them, it wouldn't be impossible for one to have found Asterisks from a long time ago or smuggled some out. They'd have to check the records and if anywhere, Kiddilon is where the trading would happen.

2) The High Summoning skill is the likeliest way for one to summon Bahamut or any of the Legendary Eidolon— If anyone knew where they are and could contact them. Summoning such an Eidolon with the Supreme Skill shouldn't take a year. Bahamut, however, is a very special case. If the Legends are correct and he's been infused with the Goddess of Death's powers, there is no saying how rules apply to him.