http://www.tcstraps.com/product/MP_XVIII_Black.html
or this one. You can't go wrong with this one.
http://www.tcstraps.com/product/MP_PAV_98.html
I really like this one also.
http://www.tcstraps.com/product/MP_P...rve_Black.html
Here is another that is a bit cheaper and has a polished buckle which would look cool on the fiver.
http://www.tcstraps.com/product/TCV_...ico_Black.html
Although a brushed buckle looks fine, and it matches the crown guard. I personally prefer brushed or natural.
The straps you are looking at are machine made, I prefer a nice handmade strap, it's more historic to Panerai.