What work authorization is best for instructor of workshops

[Lane]

Hello:

I am a Canadian. I have had TN's and an L-1 while living in the USA (as an engineer). My situation is now different and not sure what is the best solution.

I am now living in Canada. I work on contract for several employers here in Canada. I teach at one of the University's in Continuing education, as well as give workshops.

An American based company has approached me to give workshops in the US. It would mean travelling once a months to give a 4 day workshop.

I have a bachelor degree in engineering, and a PMP certification (Project management professional).

Can I ask for some advice? What work permit is best for this situation?

Thanks
Lane