Picked this up at Guitar Center for around $50, and it's well worth the price. Good for blocking vocal reflections from whatever wall is behind the mic. I may upgrade to a much larger isolation shield later, as this one is on the smaller side.
I had a larger Auralex Mudguard mic shield, but it took up too much room on my desk. This is small and fits in my desk no problem. Probably not as good as the Auralex, but I didn't have a whole lot of options.