I used to ask my wife to assist me when taking macro shots. It was the worst thing I could do. She got so interested she took it up as well. It cost a small fortune kitting her out with her gear and she's now too busy taking her own shots to hold things for me
I found the answer here:-
Search for plamp - Warehouse Express
It's called a Plamp (stupid name I know). It's made by Wimberley and it's ideal for holding reflecters, light sources (as long as they're not too heavy) and for holding swaying bits of vegetation still if there's a breeze.
It costs £30 so is definitely cheaper than finding a wife...