For the RadioShack Pro-2096 the discriminator tap is a pin as shown in the linked pic and it is labeled TP4 too. It's located on the top of the circuit board, center rear (about 1 inch from the rear of the scanner). To get to it remove the 4 screws on the back of the scanner and slide off the cover. Then remove the top half of the inner cover (4 silver screws) to access the top of the circuit board.
Rob
K9OJ