To me it is a little unclear whether for the purposes of the Commerce op the player can take the florin from the trade fair card (which is part of the market for East or West). By my reading it seems you could but it is unclear. This can be significant because sometimes there wont be florins in the face up market cards if people have been buying the cheapest cards and also because you sometimes might want to shrink the amount of money available for trade fairs.
Any thoughts on what the rule is or should be?
Take the florin from any card in the Market, including Trade Fair cards. I added a parenthetical to F2 in the Living Rules to clarify this.