Finding the Trader becomes essential after defeating Bonemass. The Megingjord, Ymir flesh, fishing gear… You need him by the time you're moving to Mountains, at the latest.
Yet finding him can be very hard if you're unlucky. I have a game going on with my 12-year-old nephew where we've killed Bonemass and are sailing around the world to locate Black Forest in which we then run around, hoping to find the trader. I'd estimate we've been doing this for about three hours (on separate sessions). I can tell that a 12-year-old finds it really boring, it's currently sucking the fun out of our game.
My solution would be that either a) killing Bonemass reveals the nearest Trader spawn or b) Swamp crypts have a chance to have Vegvisir stones that reveal the nearest Trader spawn. This would be a balanced way to make it easier to find him, imo.
Source: https://www.reddit.com/r/valheim/comments/124v8lc/finding_the_trader_should_be_easier/
