"Let's do that, then." Harry managed to reply, even as the couple began checking out Jack's work. He flashed a bright grin and handed back the portrait, mentioning, "Y'know it's usually other people who wnat my autograph, and here I am asking for yours." He didn't mind though, oh no. He always refused to autograph things anyway, as he didn't see his autograph being worth anything nor did he consider himself worthy of even being asked.
He waited for Jack to sign the portrait, smiling down at it again.
"How much do I owe you for this?" He asked, shooting the artist a questioning look. Sure, he hadn't really volunteered for it, but artwork like this deserved generous payment.