Magnetic tiles are available in our on-line store.
For $9 a set, you get tiles numbered from 1 to 36.
Here's a sample tile.
Color, as I've maintained for years, lends a bit of clarity to students. If, for instance, red tiles are used to track vocabulary and the green are for math, a quick glance at the white board will provide you and your students with additional information regarding the status of everyone's progress.
You can purchase all three colors for $25 and save yourself a couple of bucks.