I operated a retail store for 22 years, and I faced a similar situation.
My solution was to start with the number 000001, and sequentially number the products. So, I had 000002, 000003, and so on.
I used a one letter suffix to organize the products into categories. As an example, 000001A, and so on.
Naturally, I maintained lists by category.
In that way, each number was unique, and the system was simple.