According to
the TIM website, the only TIM shop in Venice City is:
Negozio TIM
Cannaregio 1412 Venezia
Tel.:041/2448525 Fax:041/5233784
Google Maps Street Level View
N.b. I've never bought a SIM there. It's been years since I was last in Italy
IMHO, YMMV, UAYOR