I don't think you need a work permit., you ara a Business Visitor.
Business Visitor
Before you jump onto this bandwagon make sure you know what a business visitor is. Business visitors must visit Canada for official business purposes on behalf of their employer without entering the Canadian labour market. A business visitor’s place of work and the source of his or her income must both be located outside of Canada.
This is because you mentioned that 1) You will work for your company which is located in your home country, therefore, the job is done purely with your company. 2)Your income isn't paid in CDN nor does it credited to a Canadian bank account. 3) Your work in Canada consists of 'meetings' with perspective clients only.
The fact that your employer 'sells' your software to clients in Canada has nothing to do with your job; "Selling" is different than "making". You should not sell them , and you are not involved with clients in Canada in anyway other than 'meetings'.
For example, if you start to document your meetings to come up with official requirements document, that's work, and that needs a WP. So make sure your 'meetings' are merely meetings and you're not involved in Business Analysts or any job related responsibility. Once you fall under a job responsibility with Canadian clients, you MUST acquire a WP.
As long as you're not 'selling' your software by yourself, and you're not elicitation software requirements to transfer them to your making work, you should be fine.
I think you should first list ALL your tasks in details, and the outcome/output of each task to determine whether you need a WP or not.