After checking Panama Canal system, booking slots available remains as per my last update:
December 15th to December 31st: NO space available
January 2018: NO space available.
February 2018: NO space available.
Next slot available:
December 15th, 2018: 1 Northbound / 1 Southbound
Alternatively to look/find booking slots available on daily basis, you can access below link (this web page is updated by Panama Canal Authorities every 30-60 minutes AGW):