Any sites or place that sells a very good and quality ladders.

Google is your friend.

Start at HD or Lowe's.

May not be in the US or Canada. He forgot to say.
The best ladders are sold at ladder-only stores, usually.

The highest quality are going to expensive. That prices them out of most of the consumer market and would be geared to mostly Businesses. First thing to look at is load capacity... how high or low that is speaks volumes as to quality. I've seen some that technically an average size and weight guy would overload.

Find something in the 350 lb and up range... those will be sturdy. And cost a lot more.

Your average retail outlets are going to have the middle to lower end stuff due to price points.

Sometimes those are good enough for some businesses... as you might go through 2 or three vs just one really good one. But replacements are easier and employee theft or general theft becomes less of a concern as they are often out in the open or on a truck or van.

If you know of any Firemen... find out what brand they use...

Check out Grainger Industrial Supplies