I have a 4.5 week old baby that seems to like to sleep with his arms out. We currently follow Red Nose safe sleep recommendations including wrapping and placing on his back to sleep. Are there any safe ways to sleep him with his arms free?

Many babies do not respond well to wrapping/swaddling & prefer to have arms free to touch their face or suck on fingers.
Red Nose promotes safe wrapping & hence our information.
He can be wrapped using a muslin wrap under his arms, or you can use a safe sleeping bag (ensuring it is not too loose around his neck.
https://rednose.org.au/article/safe-wrapping-or-swaddling-when-to-stop-and-how-to-select-a-safe-sleep-bag
https://rednose.org.au/article/wrapping-babies 
Continue to place baby on back for sleep.