Slings:
+1 with SCJagter on no sling for DG rifle.
+1 with Red Leg on
www.traderkeith.com for sling to fit PG rifle.
Specifically, I own the one called "English Leather Sling" and also the one called "Trader Rifle Strap".
Both I have used in Africa with perfect satisfaction.
Hats:
#1. My all-time favorite was purchased in a tourist type small clothing store, Kona Hawaii for 20 or 25 dollars US, about 15 or more years ago.
It is a plain green color canvas, unlined in any way (not water resistant either) otherwise typical 1920s style fedora.
I'm wearing it in my avatar but with front of the brim turned up, as per the camera man's request.
#2. I also have an Aussie style "Boonie Hat" (similar to US / Viet Nam Jungle Hat, except with a bit wider brim).
This 2nd choice hat is always in my Africa kit, in case I need another top cover for any reason - such as if a pride of lions eats my lucky fedora, or in case I need to trade a hat to Tarzan for the hunting rights to his area, etc.
Some of my friends prefer a baseball type cap but those allow the sun to fry the tops of my ears so, I cannot abide them for Africa.
Sometimes I pose with one on that has the Safari Company logo on it to appease the PH but I will not wear any hat in sunny weather for very long that leaves my ears uncovered.
Cheers.