[Chief...]

I used this product on a sidewall hole and ran it that way for a couple hundred mile with no problems.
Stop & Go 1075 30 Piece Tubeless Tire Plugger Repair Kit for Punctures and Flats on Car, Motorcycle, ATV, Jeep, Truck, & Tractor (25 Mushroom Plugs) (amazon.com)
There is a video on there that shows how it works.

 

[Chief...]

If you decide to take the tire off and patch it, I have used these also on sidewall damage (although they don't recommend it).
ZERINT TP-M13W Combination Repair Unit Kit, Tire Repair Patch Plug Kit 1/6" x 1 3/8", 1/4" x 1 3/4" and 3/8" x 2 3/8" Wrapped stem 8 pcs Each (amazon.com)
with
2 Pieces Tire Patches Tools, Tire Patch Roller and Tire Buffer Wheel, Tire Repair Grinding Head Buffing Wheel for Air Tire Buffer (42 mm) (amazon.com)
and
Western Weld Clear All Purpose Tire Repair Vulcanizing Cement Brush Top Can 8 oz (amazon.com)

Note: I did not use the buffer wheel, the sidewalls are too thin and it does not take much to compromise them. I just made sure the surface was good and clean with a little rubbing alcohol.

After the patch was installed I did put a coat of Inner Liner Sealer over the whole thing.
Steelman Inner Liner Sealer, Seals Repairs, Fast-Drying, for Tubes and Tires, Applicator Included, 16 Oz. (amazon.com)

 

[Chief...]

GlueTread Sidewall Patches - these are specifically made for sidewall repairs. A fairly new product but has received good reviews, even from the guys over at Dirt Trax. Patches on the outside. I keep a kit in my trailer now but haven't used it yet.

In case anybody is interested in ordering this, it is available on Amazon and Ebay both for about $24. But I found it on Glue Tread External Patch Kit | ChapMoto.com for $14.95.