The Miller Dynatron unit does not have to be a two hand affair. I have one that I put together that I have been using for over 10 years and it is a one hand operation that is easy to use and will start anything from a 20cc to over 150cc engine.
First, I join two 12 volt 7 amp. gell cell batteries with a couple of strips of thin double sided tape. Then using double sided tape, I mount two 2 1/2" muffler clamps on top of the batteries. I slit fuel tubing and put over the edges of the clamps to protect the starter. I then strap the starter to the batteries with a couple of large plastic tie wraps. But before mounting the starter, I remove the strip switch and add wire to connect to the added switch and bracket. This places the push button switch conveniently under your thumb for easy one hand use. And then wire in series for 24 volts. I sell the switch and bracket for $20. The Miller reduction unit is $125. I sell the complete starter for $275.