@goldenheart
Last I checked, purple albinos start at around 30k notes, and there's currently a longhair one on the CRB for 48k. If you're okay with a little more RNG, you can get a level 9 piebald cat for around 3000 notes (as of right now) and breed a purbino that way!
Edit: as for trading, a lot of people like Nestor-exclusive apparel (which seems to go for 9kn minimum?) , and if you're a big adventurer you could probably swap some business cards for your purbino.