Hey Chris, welcome to the forum!
Unfortunately, you just missed the Lake Arrowhead Classic taught by Tiffen. I'm not sure of when the next California workshop will be. Lots of international workshops taught by Tiffen this year, as you can see here: http://www.steadicamworkshops.com/
On the other hand, if you're in California, there are numerous local Steadicam operators who offer private tutorial sessions that can probably give you the equivalent of a 7 day workshop in 2-3 days of one-on-one time. I know Robert Starling offers operating workshops throughout the year, and I think Steve Fracol was offering workshops last summer. Perhaps he's becoming available again soon and willing to do so.
Also, the "certification" is more of a "you've received training from established and knowledgeable operators" thing than a certification. Perhaps if enough people prod GPI PRO, they'll host another workshop?
EDIT: whoops, also forgot Fletcher taught too! You really can't go wrong!