The area to the north of the boulevard Saint-Germain is filled with souvenir shops. Very few Parisians enter that area as the prices can be somewhat on the higher side.
You can find plenty of souvenir shops at Montmartre’s Place du Tertre - the shops are open in the evening and on Sundays.
There are souvenir shops near the tourist attractions.
There are souvenir shops adjacent to the Notre Dame Cathedral. There are book stands which line both the Left Bank and the Right Bank of the Seine River.
If you’re on the Champs Elysees, explore the Champs Elysees passages which often include souvenir shops.
If you’re at the Eiffel Tower, you can buy mini-models of the Eiffel Tower while you’re there. There’s even a post office on the Eiffel Tower from which you can post cards to friends.
Galerie Lafayette’s sixth floor has a souvenir section.
Monoprix, an inexpensive chain similar to K-mart also has a small souvenir section.
The Paris subway shops are also a place for souvenir shopping. You can buy handbags, t-shirts and scarves here at very reasonable prices.