The above link is just an example. Mine is a bit different, but all black and I believe I got it pretty cheaply from American Furniture one weekend. $15-$30 iirc. I've had it for years and its come in handy.
Something to consider if you can't find a specific attachment for your playseat, or don't want to spend as much. I can fit my keyboard, mouse mat (Goliath Razer) and mouse on it pretty comfortably.