Although assembling the unit couldn't be easier, sourcing just the right materials to ensure minimal resistance may take a little time.
Start with the magnets. Most hardware stores stock a small selection of ring magnets in packages of five or six ($4).
Next you'll need a dowel (75¢) that barely fits through the hole in the magnets (too much play, or not enough, will cause significant resistance). If you can't find the perfect size dowel, you can always sand one down, or try a colored pencil like I did. Use ultra fine sand paper for the smoothest surface possible.
The perfect straw is somewhat translucent and is just slightly larger than the hole in your magnet. Almost all (free) straws out there are of the skinny variety, so try juice shops, bubble tea stores or 7-11 for something fatter. I found mine at Dunkin' Donuts.
All other materials you'll need can be found around the house, including a suitable base and some cardboard.
Ready? Cool. Cut your dowel down to 6" and your straw to 5.25".