This also frustrates me, I vibe-coded [0] a chrome extension that reads the data from Amazon's website (read orders and purchases, which are different things...) and then matches them against the YNAB entries and then updates the memo line in YNAB with the name of the item(s) (after running the item name through a small LLM, haiku, to clean up amazon-speak into something reasonable).

This has been working well for me overall.

It's not open source (or paid), it's just for me and I'm not looking to maintain or support it but it should be easy to replicate. It does require I go to Amazon on my desktop and click the extension and tell it to "Sync" but that's easy enough and it makes my budgeting way easier.

[0] I did this over 1.5 years ago (Jan 2025) so it's probably even easier now, I wrote it with Aider and it cost $27.81 in API credits (this was before Claude Code/coding subscriptions). The only reason I know the cost so exactly is that I had started to write a blog post about it but abandoned it.