I believe there is but do a quick search of this forum because the topic has been well covered recently and there are lots of guys who would know better than me about that. Maun is still a good starting point but just not with that insane bond. I'm sure not all companies in Maun can be doing that and hopefully someone will verify or deny this.
For Tanzania, most of the charter operations are either in Dar es Salaam and Arusha, Coastal Aviation for example. There are many operators and good potential for twin time.
Best of luck.