Remote work but with a few on-site visits

Here is the scenario:

1 year contract to work for a US organization remotely from Canada. Contract permits up to 4 trips to the client site fully reimbursed.

Would I need a work Visa? The trips will always be less than 7 days. My company (sole proprietorship) would invoice the US organization.

Is some sort of work Visa required? If not, what do you say to the customs officer when he or she asks you the purpose of your trip? Would it be travel for a business meeting? The work I do is consulting.

This could work under B-1 Status if the employer was set up as a Canadian organization on the Canadian side and your compensation evolved from Canadian sources as opposed to U.S. sources. Under this scenario, a work visa would not be necessary; you would merely enter as a B-1.

There are some older blogs on here. Try typing in "remote work" as a search and you may see something that strikes your fancy.