First of all congratulations for the acceptance of your new employer or job by them. That's a step in the right direction. Second, these Canada people like documents so much. What they ask of you is a referrence letter stating hours of work, salary, duties (in line with NOC 2011), and other benefits. These must be written in company letter heading. I do understand the precarious situation the clause in your new job poses. Since you can't request for such letters, it will not be authentic if you write them on your own accord since they want it from an official of the company(e.g HR). So now, thinking on ways to get out of this situation, I will suggest you speak to one of your upline managers or senior colleague. If you can get the company's letter heading, then you can write out all their requirements on it for your supervisor to sign.(Remember that you have to be smart about it since it contravenes company policy, so you needn't make it a public fanfare). So, just make it an inhouse thing and if you're not successful, then your last option would be to explain to NSOI that company policy forbade new employees from getting such documents. Then you could ask them if your payslips will suffice for how much you earn. Then if it is in the same sector with your previous job, you could also explain that in your country, you do a standard of 40hours per week in such jobs.(Getting a government paper to back it up wouldn't be a bad idea.).
All the best.