I cannot help you with something your clients can slip on or over their studded wading boots to protect the boats bottom, but, after giving much thought to your situation, I feel that you would be hard pressed to have every size needed and your clients may not approve of using something other than what they are wearing. If they wear what you provided while wade fishing and fell, it could open up the door to lawyers.
If I was in your situation I guess what I would do is use a protective mat on the bottom of my guide boat and I do not mean some cheap throw mat. I would want something that would withstand the studs, stay put and provide drainage. I was thinking something along this line:
http://www.americanfloormats.com/wor...i-fatigue-mat/
Just a thought......
Warren
Fly fishing and fly tying are two things that I do, and when I am doing them, they are the only 2 things I think about. They clear my mind.