Sirius had almost forgotten about his date for drinks, between the party and Regulus' notes. But he wasn't the sit-at-home-and-worry sort, and there was sod all he could do short of tearing off to try to search for his newly un-dead brother who most likely wanted to kill him, anyway. If Reg wanted a go at him, he could take it. Sirius wasn't going to hide behind wards and fuss. He'd go out and get drunk with some bird he didn't know, but who seemed funny.
Sirius had realized on his way to the Leaky that he'd never really asked how old the girl was. Hopefully she didn't show up looking like one of Harry's barely-legal friends. Even Sirius had limits about corrupting the youth, if only because Harry would probably have a fit and on of the Order mums might try to castrate him with a handy sharp object.
He stepped into the Leaky, scanning the room. All he had to go on was female and redheaded, bu lucky for him the only other redhead in sight was a bloke. He took a moment to study her - young, but old enough that he was safe buying her drinks, he decided. Cute in a pixie-faced way. Nice legs.
He walked over, sliding onto the stool next to her and offering her a smile hello. "Gretchen, yeah?" he asked.