It looks like a good idea to have a portraiture done in such a romantic and artistic city - Paris; the best place in town for doing this would be the Sacre Coeur district, not the basilica itself but somewhere in the nearby. When you see the basilica, you go up on the stairs, follow the path right next to it and turn left, then you will reach to Place du Tertre where the plaza has loads of souvenir shops, restaurants as well as art markets.
It is recommended that you should come here at 12nn or after lunch time. We were here at 11am and it was quite empty. Therefore, if you arrive a bit later, you would have more choices (artists) to choose from.
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Affordable Street Portraiture Drawing in Paris
We both wanted a portraiture of ourself, and a funny one of both of us. There's another artist next door so we had our single one first by a different artist at the same time. Their stall were very close to each other. It was 20 euro each. The price was quite reasonable and they both completed it in about 20 minute.
One of the Best Souvenirs from Paris
We found out the best artist after doing our single portraiture so we asked him to do a funny one for both of us together. He is really creative and talented! We love this version even more! He turned Amy into a flower and Benson into a bee. He even drew the famous Eiffel Tower in it. This is literally the best souvenir we've got for ourselves from the whole trip.
An ultimate tip for everyone: The best is yet to come and worth your wait.