After some quick web browsing, I found a few different solutions ranging in price from $4.95 to $39.99. Being on the cheap, I mean frugal, I went with the $4.95 option from SuperBrightLEDs. The LSC-100A flashes 4 times within 0.4 seconds, followed by 4 more flashes within 2.6 seconds followed by constant light until the brake pedal/lever is released.
There are other modules that flash different patterns but this seemed to be best for what I was looking for. The module itself is small, about the size of 2 x AA batteries.
Following the factory lighting wiring diagram, I tracked down the R/Y wire (the Orange wire feeds the tail light). When I split the harness, I found the two R/Y wires (wait two? yes, two), cut them and soldered the module in place. The red wire on the side with the ground is connected to the power feed, the single red wire goes to the brake light. I crimped a ring connector to the ground and connected it to the negative battery terminal. With the R/Y wires soldered together, it was time to test before wrapping it up. With a successful test, I covered the wires in heat shrink tubing and then wrapped the harness in adhesive free wrap.
Total installation time, about 20 minutes.
(Stock pictures of the LSC-100A are property of SuperBrightLEDs.com)