Christina Aguilera has been Christmas shopping for Britney Spears two sons.The one-time rivals have buried the hatchet as the 'Beautiful' singer called Nina Takesh, co-owner of hip Los Angeles baby boutique Petit Tresor, to order presents for Sean Preston and Jayden James. According to People magazine Christina told Takesh: "I want to give them something adorable for the colder weather." The singer, who is currently on tour in Europe, chose two blue cashmere schoolboy sweaters for $129 each. Britney also called Takesh for advice on what to get the boys for Christmas.The 'Toxic' singer asked for, "something matching and playful" and chose two Kaloo chairs, shaped like teddy bears, for $85 each. Last week Britney apologised to her fans for her recent run of flashing and wild partying since she filed for divorce from Kevin Federline.The 25-year-old mother-of-two admitted she may have gone too far after being caught not wearing underwear on four separate occasions. In a statement on her official website, Britney said: "I probably did take my new found freedom a little too far. Anyway, thank God for Victoria's Secrets new underwear line!"I look forward to a new year, new music and a new me. I'm just getting started!"