An inexpensive alternative in the household is also bound to gel hydrochloric acid, as in the Johnson & Johnson Zero Zero Urinstein- and scale remover.
By curved bottle shape and the viscosity, the cleaner can safely deploy to all places and metered easily. On metal surfaces especially chrome surfaces he should not go. To clean the toilet with this cleaner, I use only one extra brush set plastic. Some of these brushes are heated in new condition with the heat gun and bent and cut to the bristles, so that you come to every conceivable place. Upon completion of this massive cleansing the extra brush set is kept closed in a diaper box in the garage.
Finally, please note such an acidic cleaner does not destroy the glaze of the ceramic as scouring powder or alkaline cleaners.
Even if I can not do much with the somewhat nebulous term "urine scale", there is for effective and in many ways very gentle for the ceramic of the toilet cleaner, a strong buy recommendation!