So you want someone you do not know to say they are inviting you to visit Canada and in doing committing a fraudulent act ?
Also you should only ask for a 2-3 week visit maximum ,How long you can stay will be determined on arrival but the longer you ask for as a visitor the greater justification you need.
An invite letter is not as critical as showing you can afford the visit , that in paying for the visit makes sense in terms of your financial position and that you have ties back to your home country that shows you will not overstay.
The majority of people visiting Canada do not know anyone in the countrt but they are able to demonstrate genuine visit intent without a supporting letter.
Why do you want to Canada anyway and do you have day by day visit intinerary for 25 days ? So basically actual purpose of visit that you stated in your application.