A seamless Voronoi F1 Smooth Euclidean Formula noise map pack. Invert it for a "billows" like effect. Enjoy.
Download 32bit Float EXR Pack (346 MB; maps at 4096x4096):
https://drive.google.com/file/d/1Vz3CeSIU6IupRx3T08wMICiEScfdLmC4/view?usp=sharingPack includes 6 maps with smoothness levels 0.25, 0.5, and 1 in two flavours; semi-random, and full random.
PS few little peaks that are too sharp for my taste, (the block spots you can clearly see), but you can easily use a clamp minimum scalar on it and get rid of them to be more uniform with the rest.