get an old game card these are fairly common at any PC junkyard
pull the NE558 chip and the 4 timing resistors
replace the resistors with jumper wires and
jumper the NE558 socket outputs(4 corner pins 1,8,9,16)
to the inputs(next to the outputs 2,7,10,15)
now what to do with the write/clear timer strobe output
available on the NE558 socket (paralleled to pins 3,6,11,14)
strobes on any write to port 0x201