The Cubs offered weekend passes for the 2017 Cubs Convention through pre-sales available to season ticket holders and a second open to Mastercard holders. The weekend passes then went on sale to the general public on Friday November 18th and by all accounts, each of these three rounds of sales were complete sellouts within minutes of their respective start times.
As of this time, hundreds of passes are available on Stubhub but if you have to go this route, be prepared to pay a huge premium. With Stubhub's fees tacked on, passes will cost at least $440 each!
There are also a few passes available on Craiglist that may be cheaper than Stubhub, but buyers beware that there are no guarantees the passes being sold on Craigslist are genuine.
Hopefully you were lucky and got the passes you needed. The 2017 Cubs Convention is not to be missed!