Aurender Flow is the only sort of, almost, kind of, DAP (not portable, as in, desktop use only) I can think of... Although it does raise the question of why? MicroSD is far smaller and lighter, physically, easily hot-swappable and I can't think of a situation in audio where the speed gains from an SSD are of any benefit (maybe if you're constantly refreshing your entire library?). Not to mention then power draw!
Care to share why? For better suggestions
As a laugh, I did manage to connect an external HDD to a HiByOS based player (Shanling M2s) with a powered USB hub, but that's probably not what your asking for! lol
p.s. there's probably WAAAY more options for DAPs with a 2nd mSD slot if storage capacity was your main concern. But I guess you already knew that...