There are many chemical companies selling Sodium Chlorite in Canada. And all that's needed to buy directly is a registered business and a legitimate reason to use it. In our case, we use it for cleaning and water purification.
Until recently, several of these companies used to sell to the general public. That is of course, until the product sale advisory came out. After which, they are now forced to ask for prerequisites to fulfil orders. ie, the company type and purpose must show relevance.
That being said, many cleaning companies prefer using Chlorine Dioxide for it's rapid dissipation properties which work well with septic systems and the fresh air scent it leaves after use. As opposed to other cleaners and bleach products. I myself make extensive use of CDS in the lab. Which has proven to be indispensable in cleaning lab glass and other items used in the production of Colloidal Silver .