Greg,
My search has not yielded any information on the company. Perhaps the thought was to form a company made up of men from Waterloo and Eastport since they were so close (by water). Both James Hamilton Witherspoon and Hiram Richardson are buried in the Richardson Cemetery in Waterloo. Witherspoon would have been to old to serve, and I cannot find a record of service for Richardson. In 1860, Richardson was a 30 year old teacher living near Green Hill with his mother and several siblings. In the 1870 and 1880 census records he is listed as a merchant in Waterloo. Here is a portion of what is said about Witherspoon on his FindAGrave memorial:
"Rev. Witherspoon was in the mercantile business in Waterloo all his adult life. He also built a cotton gin, grist mill, and saw mill. He was also listed as a farmer in the census. He was also called Major Witherspoon and occasionally represented Lauderdale County in the state legislature. He was a local preacher. When the First Presbyterian Church regular pastor was absent from his pulpit Rev. Witherspoon would fill his place and the congregation was glad for they knew they would have a good sermon. This was reported by one of the officers of the church regarding Rev. Witherspoon."
A search for information about Eastport yielded a book that might have more information:
https://www.amazon.com/Gunboats-Cavalry-Eastport-Mississippi-Emphasis/dp/0943054400