I was thinking when I read your post if it was possible to make your own whiteboard cleaner. I have all my work done for the day so lots of time to play and research. Off I went and found this tutorial: How to Make Dry Erase Board Cleaner | eHow.com
I don't know how well it would work. Instead of Orange Zest I would think Orange essential oil would work better. Make sure you get real essential oil and not fragrant type oil for decor. Essential oils are completely different.
I also found this article: Homemade Dry Erase Board Cleaner | LoveToKnow
One more tip after using a homemade dry erase board cleaner I would give your stamp a good coating of glycerin to protect it from drying.