How can I turn off passenger airbags for child seat?




I've read a few posts on the search but I cannot find a definative way to turn of the airbag on the passenger side for a child seat?
I callerd the stealership and they said that they only way is to buy a Mercedes Child seat which has an imbuilt transponder that will deactiveate the passenger airbags, but seriously who is going to want to buy another car seat when they have just bought one already? I asked if you can buy the transponder seperatley but they said no.?
Does anyone know if there is a fuse or wire or anyway to de-activate the passenger airbag?
Thanks







