That looks really nice.
There are quite a few dwarf yellow water lilies, many of them sold in department stores and in little bags in big nurseries. Of course, purchased that way they might as easily be pink or white when they come up, despite what the picture says.
The places I used to purchase water lilies from have shutdown. I often trade online. My only yellow water lilies at the moment are young and came from specialty breeders ($$$), so I don't have any to trade at the moment, sorry.
For yellow varieties, I've grown Helvola, or Yellow Pygmy, which was tough, stayed small, and is commonly available. Chromatella is popular and has slow growing rhizomes, so doesn't outrun it's pot so fast--I had an unknown at one point that I think was Chromatella, but not sure. Mexicana comes up with mixed reviews. I knew one person who had it take over their pond completely in a couple seasons, but others have told me it's not so bad, so I don't know. I haven't grown it.
And if you want to try something fancy, water lily breeding is experiencing a renaissance, and the number and type of new varieties have exploded in recent years. Stay away from site like Bergen unless you want to be enticed--I go there for lotus, but come away with water lilies sometimes. They always deliver great plants, and they grow all their own stuff, so their description, while sparse sometimes, are from personal experience. And I can point you at sites that sell plants (good stuff, new imports, I know them) for up to $200 if you really feel rich.
I could send you some of my beautiful peach water lily that I'm always trimming back, but it's a thug and grows like crazy (blooms heavily, though), so probably not what you're looking for.
Maybe we can get others in the community to chime in with their own sources. This place gets a bit quiet during winter in the northern hemisphere.