try using clear soda bottles. Cut the bottoms off two different bottles, remove the lids and secure in the middle with a large wooden bead that has a hole drilled through it. Secure it all with your favorite adhesive (I'd turn to E6000) and continue with the rest of the stool assembly.
This 30 Minute Hourglass Sand Timer makes an elegant accent for a vintage style home office or kitchen. Inspired by nautical ship hourglasses, the aged metal frame adds a unique touch to this large timepiece. Time is approximately 30 minutes, but may vary.
Three Tier Five Minute Antique Wood Sand Timer - 9 Inches Tall This three tier five minute timer has a history as unique as its style. The timer is composed of antique wood spools found in abandoned textile mills in England. The spools were used to hold thread, cotton, and yarn that were spun into fabric. The spindles and wooden base date back to 1907-1913 and were used in a factory in Calder Valley, Yorkshire which wove the thread into a cotton tartan fabric.