Easy DIY - it's been holding up for a week, and I expect it to hold up well in the long-term.
The mesh (I presume polyester or nylon) fabric on the BMW e93 wind deflector (i.e., BMW part number 54347269437) is easily torn or ripped.
I found a product that seems up to the job to fix at least smaller rips. My rip was about 1 inch by 1/4 inch, and close to the edge of the wind deflector.
The product is Gear Aid Tenacious Tape (black). It is available through Amazon
- get black!
I simply followed the instructions on the package, severely over-estimated the size of the tear, and applied the tape as shown in the attached picture. If it holds up in the long term, then I won't touch it.
If it starts to peel away, then I'll reapply with tape on both sides of the wind deflector fabric. If this happens, I will also cut the tape to a more appropriate size (I left it at it's natural width in the picture - too large for my rip).
The color/fabric blends in quite well, and the tape is advertised as working well with mosquito netting and camping gear, so here's hoping it holds up!