Spoke to Weber Customer Service
I ordered and received my smoker 2 weeks ago and after smoking a few slabs of ribs and preparing to modify my grill for the insertion of temperature probes I noticed the thread posted on the Virtual Weber Bullet homepage and was disappointed that I did not wait. That having been said, I have been on the phone with a customer service representative from Weber and after explaining my situation and the desire to install a grommet in my weber smoker was told by Weber customer service that they could not knowingly supply me with the grommet if my intention was to retrofit it into a grill that does not have the hole for it.
Since I already used my smoker, and don't feel like trying to switch it out for a newer model, I am now working on acquiring the grommet using Weber's part number (85037 - Grommet, gray, SMC) as it is listed for all three of their new 2014 smokers (14", 18.5", 22.5"). I hope to be able to acquire it in the coming week. Weber customer service did say the part was available, just not how to go about ordering it.
Also of note is that the grommet is listed both individually and as part of the hardware package on the new schematics on the Weber website (these are for the 18.5" WSM):
83196 - Hardware SMC with grommet '14
85037 - Grommet, gray, SMC
I am planning on using a step drill bit to make the hole, as a punch of that size would most likely indent the surrounding metal due to the curvature of the center section.