I love it when I see a cool idea. These would be pretty easy to make. Would buy them if they were 1/3 of the price but $30 is too much. 2 Hobo Tin Can Beer Holders/ Garden Drink Holders. $30.00, via Etsy.
There is an extra tack down in the small square of the design intended for a piece of vinyl or like material that you can use a dry erase marker with. Chalkboard fabric will work too! appliquealley.com