From FOnline: 2238 Wiki
- You can occasionally find lockers in random encounters on city ruins terrain, some of which can be trapped. Opening these usually requires a high lockpick skill and may contain items ranging from a worthless Junk to Blueprints. Some of them cannot be picked.
- There are Quests that may give Blueprints as reward for your efforts.
- Trade with other players.
- Consult the Blueprint Hunting FAQ for more info about hunting blueprints in the wild.
For a list of items requiring blueprints, see here.