An umbrella and a plastic poncho may come in handy in the “rainy season”.
Ear Plugs might be of help to light sleepers because Lisbon is a noisy city. There are people on the streets in the early morning hours largely due to the fact that city’s nightlife starts and finishes late for locals (and tourists alike), especially in the most tourist areas like Bairro Alto, Baixa, Belém, Chiado, Parque das Nações, etc..
To obtain Euros in advance is useful for paying for small items, gifts and food with cash, if desired.
Medical Supplies are not needed during the stay in Lisbon. It is always cheaper to buy local brands. However, all prescription medications for allergies and other diseases of certain brands are a must-bring.
A pair of sunglasses, sunscreen, after-sun cream and hat should be always in hand no matter it comes to a walk around the city or sunbathing on the closely located, sandy beach. The sun of Portugal is very heavy, especially in summer months.
A good and comfortable handbag for all necessary belongings and documents is a must. It must always be held in front because of the numerous pickpockets everywhere, especially in tourist spots and on the metro.