There is no Scottish 'trick or treat' tradition; on the contrary, 'trick or treat' may have its origins in the guising customs.
Halloween, known in Scottish Gaelic as "Oidhche Shamhna", consists chiefly of children going door to door "guising", i.e., dressed in a disguise (often as a witch or ghost) and offering entertainment of various sorts. If the entertainment is enjoyed, the children are rewarded with gifts of sweets, fruits or money.
So, looking for your very own guising costume? Then this should do the trick!!