Although it is not specifically labelled as “blagging”, Draco Malfoy commits this foul on Harry Potter by holding on to the tail of his Firebolt during the Quidditch Cup final in their third year (PA15).
Blag means to get something by using guile or persuasion. It can also mean to obtain it by robbery (Oxford English Dictionary).
Lexicon list of Quidditch fouls
From the Web
Writing by J.K. Rowling on Pottermore: History of the Quidditch World Cup
Harry Potter Wiki: Blagging