Many of the patterns can be obtained from specific missions as a replacement for the season they were a part of being removed. The remaining ones are mostly either from xur or raids after that. Xur is entirely random so I hope you are lucky. Raid weapons are a pain to use deepsights on because you need spoils of conquest AND a deepsight to get a red border. I personally used to save non deepsight raid drops in my vault until I had the spoils. Otherwise you could end up with the spoils and deepsights, but not the weapon to use it on. Bottom line, don’t use deepsight harmonizers on weapons you can get from a mission or a destination. Save them for xur and raid weapons. Since those are much harder to get the value is much higher.

The two main sources are Raids, except Desert Perpetual and Exotic Missions with the Classic Collector modifier selected. Take a look at the following Monument of Triumph | Legendary Loot Sources: [url]https://docs.google.com/spreadsheets/d/1WDj-vExf9c982PVc1nRRfjadhkcZFqa7nv14cCMI8C8/edit?usp=sharing[/url] It breaks down where loot drops, including the sources where craftable weapons can drop.