I have experience. I have visited Portugal (lisbon many time)
The best bet are two i quess they are agencys but have independent girls called escortprivada.com and you will find the website. The pictures are real, and Megan from their agency is amazing.
Otherwise there are some small brothels but these are shaky. In most of the higher class hotels in the city center around 22.00 start appearing also call girls to the down bars. I have tried them many times aswell.
But your best bet is that agency
Its actually independents, they have their own numbers up on that agency site.