Update 21-Apr-2014: After more than a year and 2500 miles, the repairs looks to holding up well. I can't tell for sure without removing the control arm, but installed there are no visible openings in the boot.
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While installing the H&R springs, we tore the rubber boot on the rear lower control arm (Part number
99333104301). This was easy to do as the rubber was clearly worn around its typical crease position.
This ball joint is press-fit into the control arm with the rubber boot as an integrated part of the assembly. Despite significant effort, I couldn't find anyone who could replace it, or any boots that even came close to having the same design. (If anyone does know of either, leave it in the comments!). The other option is to replace the entire assembly, but that is over $200 to fix a worn boot!
After a bit of searching on the web, I found two different suggestions for dealing with this issue: 1. use silicone sealant to repair the gap or 2. make a patch with a bike tire tube.
My plan is to try the silicone sealant first, and fall back on the bike tire tube if necessary.
Here are the steps I followed.
1. Rough-up the area to be patched with some fine-grit sandpaper (I used 1000 grit).
2. Clean the area. I used an alcohol swab. I doubt this is the best cleaner, but figured it was good enough.
3. Apply the silicon sealant.
4. Smooth out the silicon sealant. One useful tip I read online is to wet your finger with water. I was amazed at how well this actually worked.
Here is a look at the finished product. I will keep an eye on its durability and post back how well it held up.
