Teen pop sensation Justin Bieber is reportedly buying a diamond ring for his on-off girlfriend Selena Gomez. The 19-year-old singer asked a Beverly Hills jeweller Neil Lane to design a 650,000 pounds creation to be gifted to Gomez on her 21st birthday, reported Daily Star. Lane has supplied engagement rings to stars including Madonna and Britney Spears. Teen pop sensation Justin Bieber is reportedly buying a diamond ring for his on-off girlfriend Selena Gomez. "Justin is planning to go through final designs with Neil in the next week. At the moment his favourite idea is a huge, canary yellow, princess-cut diamond surrounded by smaller diamonds and set in white or yellow gold," a source said. Bieber is known to have kept his concert schedule clear for Gomez's 21st birthday. He is planning to fly back home from Boston on July 21, a day before her birthday. Bieber has behaved himself since they reunited last month when she flew to join him on the Scandinavian leg of his 'Believe' world tour.