I remember seeing rubber balls about the size of a bocce ball filled to a high pressure with helium. Not enough buoyancy to float, but they definitely took off when you chucked it at the ground
I thought this would be the case for me, but when we decided not to for our son, only one person we knew agreed with it. The crazy part is most people would start by saying something along the lines of "ooh it's a boy, how's it going down there?" Like they feel bad about it. But when I tell them we didn't suddenly its all about hygiene and aesthetics.
Also surprised at how many people asked about it...
If you're ever in Stockholm, there's a whole museum dedicated to the Vasa. Definitely worth a visit. The ship is way bigger than you think