Osprey Games sells watermarked PDFs exclusively through . This is the gold standard. You can buy the Stargrave Core Rulebook PDF here. Currently, the core book does not have robust solo rules, but it has the foundation. Price is typically $20-$25 USD.
Use plenty of scatter terrain and line-of-sight blockers. Sci-fi wargames with firearms turn into instant "kill boxes" if the map is too open.
