Sales volumes are difficult to find, explicitly broken out would be difficult, however if you look at staples such as soft drink distributors or restaurant's quarterly reports, you can get a basic break out. The first two to look at would be Coca Cola and Pepsi:
Looking on YCharts, this gives you a quick view of seasonality, but you only get ten page views before you must register.
Publicly traded restaurants can give you an idea of additional seasonal variations:
- Darden Restaurants
- Burger King
Electronics are difficult as there is such variation
You can find the open source versions from their respective Quarterly Earnings Reports: