If bicarb doesn't work, Young Living make an essential oil called Purification which is magic. Just a drop or two mixed with water and sprayed over the area will not only take the smell away, but also make it unappealing for dogs to use again.
The ingredients are Citronella, Lavandin, Lemongrass, Myrtle, Rosemary, and Tea Tree if you want to have a go at making some yourself. (Lavandin is the oil from Lavandula hybrida, which is significantly more pungent than Lavender, which is from "English Lavender", Lavandula angustifolia). They publish the ingredients but not the ratios, so I can't help you with the latter!