Note: I post the links to Amazon because it is convenient to do so. I didn't necessarily buy the items from Amazon, nor endorse Amazon.
I use tripod quite often, so I need an Arca-Swiss Quick Release Plate by Cowboystudio (you can tell that I'm cheap
) ->
linky.
The sling strap is Op/Tech ->
linky.
I just use the above as is. But if you are a big guy, you may need the whole thing (with the shoulder thingy) ->
linky.
To make the "hand grip" adjustable, I use an Op/Tech webbing connector attached to the quick release plate ->
linky. For better photo and description ->
linky.
Read this thread ->
linky.