Tanaka by general consensus seems to have fairly good 2-strokes. Although for the sake of convenience due to not having to mix gas and oil, and also due to generally running quieter, and burning cleaner and more efficiently, 4-strokes have the advantage here. Golden Eagle offers their kits both with 4-stroke and Tanaka 2-stroke options. Stihl 2Mix, if you can adapt one of those engines to either a Golden Eagle belt drive kit sans the engine, or a friction drive kit for the sake of simplicity, from what I could tell, seem to be fairly well-designed 2-strokes as well. A lower-displacement 4Mix (4-stroke that uses gas/oil mix like a 2-stroke for the sake of saving weight, I believe) would work there as well.