I had one of those foam arm rests. It lasted about 2 months. The elastic bands that hold it to the cup holder stretched out and it barely fits the cup holder opening width wise. This same ebay vendor I purchased it from refunded me the price minus the shipping charge. It's the same one 86Speed sells but cheaper.
http://www.ebay.com/itm/Sports-Cente...9SlX2w&vxp=mtr
Get one of the oem ones and like Dadhawk said use 3M double sided tape to install it if you don't want to drill.