Chapter 22 of Order of the Phoenix contains this alarming line (emphasis mine):
"That’s right," said Sirius encouragingly, "come on, let’s all ... let’s all have a drink while we’re waiting. Accio Butterbeer!"
He raised his wand as he spoke and half a dozen bottles came flying toward them out of the pantry
To memory, this is the first time that he is shown with a wand and it is widely presumed that his old one was snapped after his arrest. So, how did he - a very wanted man - get a new wand that suits him?