I don't think this domain has value even as a URL shortener, because there are plenty of alternatives on the market. 1-letter domains are not that rare even in ccTLDs.
Most African ccTLDs are underutilized and have low registrations numbers.
To give you an idea, I sampled the .bw zone last year and there was something like 4000 domains registered. It's not bad by African standards. Eritrea has less than 100 regs I think...
There is no information about the registry. Even the ownership requirements are not clear.
Also, there are not so many .bw registered at the second level.
The most common form is still .co.bw.
Perhaps this will change in the long run.
On the plus side, Botswana is a fairly respectable African state with a long history of democratic rule and political stability.
I think you will struggle to find a buyer, and if there is no buyer how much is the domain really worth ?
PS: have you ever seen just ONE single reported sale for .bw domains ?
And if you must pay $300 per year in renewal fees, that makes the purchase even less interesting. The extension is exotic and expensive to keep.