Stellaland was the first Batswana area to issue stamps, in 1883. As the self-declared Republic of Stellaland, the entity merged with the similar-situationed Goshen to form the United States of Stellaland. Stamps were issued by Stellaland until 1885, when the British took all of Botswana and turned it into British Bechuanaland.
There are generally a few Stellaland stamps for sale, though finding an example for real cheap might be tougher. But, realistically, the stamps from this era are of such historical interest and fascination for collectors that it’s ok to splurge a little on a Stellaland stamp for sale.