Artist, Scavenger, Magician… Sobrero scours Europe for the arcana of his craft. A camper was for years his field headquarters as he combed the countryside for fleamarkets and purveyors of bricabrac, rooting out "items in glass, in wood, in metal, small animals, busts of famous literary figures, musicians, or historical figures, hats … bas-reliefs, and musical instruments."     Collecting is a continuous passion and Sobrero's home in Milano is filled with stores of curios to draw upon. But a special commission can set him off on another quest at any time. Commissions can sometimes be very obscure; there was one, for example, on the theme of the rhinoceros. "After dozens of telephone calls, long research, and the odd journey, the result was really very satisfying."     Beyond collecting, Sobrero nurtures relationships with specialized artisans --the Venetian glass maker who will make him tiny vases, the master of leather gilding who will finish the miniature bookbindings with gold titles. The basic structure is crafted by a carpenter following Sobrero's detailed plans-- usually a bookcase but perhaps a diminutive desk or display case, an alchemist's workbench, a cook's pantry…      "I build practically nothing myself," says Sobrero. "I'm just a miniature decorator." But this humility belies a magician's sleight of hand, for each tiny detail is perfectly chosen and placed, each seemingly casual cluster of objects perfectly composed.