I bought a bunch of
these on Ebay, and attached them to a baby gate at the laundry room door, and to the diaper changer.
Or these, but you'd need a way to keep it secured to the table.
http://pinterest.com/pin/120612096240548168/ Ours is slid between two bars and leaning against something behind it. It comes out easily, but the babies just stand in front of it and open and close the little doors.
Maybe buy a small used wooden end table and attach some things to it to make it an activity table?