While a bottle of hydrogen peroxide or betadine could remain in your cupboard for a year, it may only last a few days at the shelter as there are so many animals to treat.
If you want to go there before visiting the shelter:
Farmacia Araceli Martínez Sastre.
Carretera de Málaga, 105.
29.120, Alhaurín el Grande (Málaga), Spain.