Mylar tinsel is difficult to find except when winter decorations are in stores. During this time larger chain drugstores, craft, party planning & discount department stores and even hardware stores may carry Mylar tinsel. For the rest of the year a suggestion would be to purchase sheets of Mylar found at craft stores. These sheets of Mylar can be found in the gift wrap and gift basket supply isle. You can use a paper cutter or paper shredder to cut the sheets into strips like tinsel.
Hunting/fishing shops sometimes carry mylar tinsel as a fishing lure.
An alabaster box is a box made of alabaster (a mineral). To find out more about alabaster, please see this site: http://en.wikipedia.org/wiki/Alabaster
In New York City, Lucien Freud is represented by the Aquavela Gallery. I don't have the details but it is located on E. 79th St between Park Ave. and Madison Ave.