That is certainly not an easy decision.
You may want to check out the
"Reference PAM STRAP GUIDE"
Here are also some examples for you to consider. (from P.com)
Rubber
Black Leather
Gunny
Cracked Vintage Leather
PAV
Black Croc
Ammo
Snake skin
There are a lot of choices, it all comes down to personal preference. I hope you find what you're looking for. Any type of leather, appearance, style of strap, I am sure the strap makers can make one for you. Good luck!