Add on to strap to make it more comfortable?

Murphy  Some people like the "black rapid" strap as it lets the camera slide to your hip during carrying instead of to your front. It is great for cross body carry without sacrificing easy accessibility to the camera. The connection simply slides up the strap as your bring the camera into shooting position. Be aware that straps that use the tripod mount as the camera/strap connection have been known to pull the mount out. This seems more of a danger for heavy lenses.

In general a wide strap is more comfortable than a narrower one since it distributes the weight of the gear across a larger surface. If the neoprene of your current strap rubs your skin you might be happier with a strap made of fabric instead of neoprene.

My favorite strap is a very old cotton webbing one that came with a canon camera from pre-digital days. My other "cute" one is a tamrac strap with tiny photographers on it. But it isn't all that comfortable for a full day of using it as a method of carrying my camera. www.amazon.com/Tamrac-Slim-Camera-Strap-Flash/dp/B000HIAJEC/ref=sr_1_9?ie=UTF8&qid=1443279986&sr=8-9&keywords=camera+strap+tamrac I use my strap as an insurance against dropping and not so much as a method of wearing/carrying it.

Given your need for speed I'd order through Amazon and double check the handling times/delivery. Most camera gear orders aren't quick turn around. Your best bet might be a nearby camera store instead of online, or plan your first stop in NYC to be at the B&H superstore!