How would you compare the Purple Mink to the Purple Haze, if you've tried the Haze? Both seem interestingSoft synthetic brush and you like the Rainbow Pony…
As already stated: The Wald A1. There is nothing like it.
I understand that the Wald is beyond your price point at this time, so I’ll throw out some other great options that do not cost a lot.
Yaqi Purple Mink: very soft bristles, short loft, so no tangles
Yaqi Arctic: the white knot in a semi translucent sea green handle: very soft bristles.
Yaqi Evil Zebra: looks like a reverse tuxedo knot, bigger knot (26mm), soft, good density.
Good luck with your search.