Motohaus, León S.A de C.V.
Av. Paseo del Moral 338 Local 13,, Col. Jardines del Moral, C.P. 37160 León, Guanajuato
01 (477) 717 67 67
This is the nearest BMW dealer. Give them a call. You will probably find someone who speaks English. They will be able to get you a BMW battery for sure but it will cost a LOT of money. Ask them if they know where you can find a YUASA.
Hope that helps.