Dummy filler card for X220 express card slot

[bbin5]

After reading several forum posts about the risk of cracking the left palmrest area on the X220 due to an empty express card slot underneath, I would like to fill this slot with a dummy blank card. For those that have done this, any specific brand or model that works best with the X220 chassis?

Ebay offers several of these blank cards by Dell, HP, etc. but they all look slightly different on the front face and I wasn't sure if they would fit properly.