This is my model of a balloon which can be printed in any color you like, as many as you'd like, have them your way !

The model profile is designed to be printed with mostly only 1 wall, very thin, so that if you choose a filament which is translucent (my Sakata orange did a good job for this), you will see some light being diffused, as a real balloon would do !

The base has an 1.9 mm hole, in order to receive an old bit of 1.75mm filament scrap as the cord of the balloon. You just have to turn a sharp knife once or twice to clean the hole postprocess, don't overdo it, as the hole easily gets slack. Because the model is without filling, there is only one one layer to stop the filament, if you break it, just use some glue I guess if your balloon slide down your filament.

The model for the heart shaped pot can be found here : https://makerworld.com/en/models/154475

Even though the model is only printed with 1 wall, it is surprisingly sturdy, like an egg shell, up to some point, of course !

I had to put a bit of filling on top, so the more horizontal layers of the model top could be printed correctly, without any holes.

The 0.08 mm layer height is to ensure a top as round as possible, with as less top filling as possible.

You could probably print this model @ 0.2 mm layer height, haven't tried it, and/or with filling if you don't need the translucence.