I can't run the first couple hundred episodes' source because I haven't found those assets anywhere in the files I got when I preordered. Are they available somewhere?

If you follow the sendowl link, there is a "Legacy Files" folder and in that there is a "Handmade Hero Legacy Art Files" download (handmade_hero_legacy_art.zip).
In that zip file there is a "early_data" folder containing the test folders (bmp and wav files).

OMG I feel stupid!! Thanks!

@Simon Anciaux The link is not working can you please update it. Thank you.

It wasn't a link, it was just the name of the file to download if you purchased handmade hero and got the download link. We can't distribute the files, you need to purchase Handmade hero to get a download link. You can buy it there: https://mollyrocket.com/#handmade