I know this thread is about a year old, but I'll post what I found anyway.

I too am looking for Cox's Landing and Boulware's Wharf.

Consulting civil war maps at the Library of Congress, I found two that show Cox's Landing, on the east bank of the James just south of Ft. Brady.

http://www.loc.gov/resource/g3884r.cw1038000/

http://www.loc.gov/resource/g3884r.cw1037000/

Still don't see Boulware's Wharf.

Also you will find various accounts of how these exchanges took place in:

The War of the Rebellion: Official Records of the Union and Confederate Armies

http://www.civilwarchest.com/officialrecords

These are the official correspondence from both sides. I found some very descriptive entries related to the subject.

http://www.civilwarchest.com/official_records/S2-V08/300

Hope this is helpful. Was to me.