Rad always flat

The wheel of the stroller always lost air and I could find no hole (water submersion). Wanted to buy a new hose, this dimension but get nowhere.
Thus, the Dichtmitteolbestellt, valve taken out (unfortunately can not be helped - even with car valves !!) means filled and now the tire is after more than 2 months still hard as at the beginning. (I used to inflate all weeks)
Just great - oh yes the shops here have something just in the pressure bottle, and for car tires - dosage according Seller almost impossible - in this product is no problem