Rob Potterton is a reputable nursery in Lincolnshire, England.
http://www.pottertons.co.uk/pott/browse.php?folder=201
They sell Colchicum autumnale but you will need to check with them about importation to Brazil.

it less likely at this time of year. they go on sale in the uk in late summer [july/august]

Of course, Brazil is in the southern hemisphere so it is approaching 'late summer' there now. Difficult to buy the bulbs in the northern hemisphere now as they are starting to put up leaves. You will probably have to look to southern hemisphere suppliers, momochan.