I just checked ebay and there is seemingly an endless listing for them, anything from $.99 to $11.00. Some mount to the bottom of the kickstand and cost around $25.
On my Vulcan Nomad I affixed a hockey puck to the bottom of the kickstand pad. It was primarily to help it sit more upright. It sure helped on soft pavement too though. We did it at my Canadian friend's home in Castlegar, BC after my kickstand sunk into soft asphalt one day in July while we were waiting at a construction stop. The stuff was probably an hour old.
My 3T sits much more upright so I couldn't attach anything. I just use a 5 inch round plastic pad I picked up free at a bike show. I have a hole drilled in it and a length of string that I wrap around my mirror or brake to ensure I don't ride off and leave it.