I like nastursiums too but they do not like our heat. I have grown them early in the season but can't count on them once the heat starts. I have found planting them where they get some evening shade helps them last a bit longer. I really like the trailing types and the variety Alaska with it's variegated leaves.Oh, and I bought a silly amount of Nastursiums seeds - 8 varieties from 3 sources. I even found trailing Nastursiums at Johnny’s seeds. Nastursiums are edible, grow well, and are pretty until a hard frost.
Have you ever tried this company?
https://www.swallowtailgardenseeds.com/annuals/nasturtium.html
I've bought from them many times. They ship promptly and have $5.99 shipping. Everything I've bought from them grew very well.
They have several types and some trailing types too. The trailing one called Moonlight has yellow blooms. I really like that one.