PA-32 pilot reported as they entered the pattern according to Tower's instructions a banner tow aircraft they were unaware of reported a NMAC with them.

Narrative

We were approaching ZZZ from the east along the shoreline at 600ft AGL. At approximately; 10NM east of the airport; ATC advised us of traffic ahead (between us and ZZZ) at 500ft AGL and 900ft AGL. In response; we replied that we would climb to 1;500ft AGL to avoid. Thereafter; we were instructed by ATC to change frequency to tower. We complied and initiated contact with tower. Tower instructed us to fly toward the bridge (nearby) and enter into a right base to land. We began our descent to pattern altitude (approximately 1;000ft AGL). Soon after arriving at 1;000ft AGL a banner tow plane made a radio call stating that he had a near miss with another aircraft (he called out a different tail number). As we turned base to final; the tow plane then stated that he believed it was our aircraft rather than the initial one that he called out. We didn't see the tow plane until we were on the ground and clear of the runway. We made a call to tower and they said that they believed the near miss occurred approximately 2 miles east of the airport. They did not have radar.