Not cheap or easy to get, but the best stuff I've ever used (on a high end car I used to own) was ordered from Dynamix in the UK. I had to send them a small interior piece that they could custom match. But that stuff was AMAZING. I used it to touch up a leather door handle, and it never wore off. Also, you applied it with a brush, so there was no overspray & no extensive masking needed.

As an alternative, those spray cans at Autozone can work. But they tend to rub off over time, and they only offer like 4 colors, so you'd have to paint the whole door trim panel (and the other doors to match).

Sorry I can't be of more help. Hopefully someone will chime in with a brilliant answer!