Where do I find an online, full-text, english version of the most
recent constitution for the Republic of Botswana (in Africa)?

I was able to find an outline at 

  http://www.ipanet.net/documents/WorldBank/databases/botswana/bo1pls11.htm

Several other summaries of Botswana constitutional law were found at
websites such as http://www.loc.gov/law/guide/botswana.html

I did find contact information about the Botswana Parliamentary
Library.  They can probably help you with getting a hard-copy of the
document.  Botswana is an English speaking country, and they have a
decent telecommunications infrastructure so contact shouldn't be an
issue.

Botswana National Assembly Library
Parliament Buildings
P.O. Box 240
Gaborone
Botswana
Tel.: *(267)373200 ext. 216
Fax: *(267)313103
Telex: 2376 PULA BD
E-mail: parliament@gov.bw