.041 and .0415 (41's) are the only chain sizes I hear mentioned on kits, an expert will pop in here in a moment to set that straight.
But, these are little 50 cent items, available at a variety of mom and pop operations, perfect for picking up and getting "local notice" about your hobby. Ag supplies, hardware stores, five and dimes, bike shops.
That small stuff is perfect conversation starters, and a perfect place to get the right chain sized, without buying a chain breaker or doing any grinding.
The more locals you can get talking about your hobby, the more the the auto driving public becomes aware of your presence on the road.
In other words, that 50 cents gains you a bit of benefit and plenty of advise if a problem pops up.