Whatever you do don't buy your replacement slats in Ikea!
For the simple reason that Ikea beds are slightly bigger than non-Ikea beds, so unless your bed is already Ikea their slats won't fit it.
(As it happens I have an Ikea bed, with their slats, and it's amazingly comfortable. My last bed also had wooden slats, and I'm using the same mattress, but I get a much better night's sleep now. I'd highly recommend them.)