Big caveat: the Hardlight is by all accounts just an “okay” gun. Like, if you had no exotics at all, and you found this one, sure, use it, but if you have other options, you’ll probably never chose this one. I’m mostly interested in it because it’s one of the last exotics I don’t have. Also it apparently looks and sounds really cool. But as utility goes, you’re probably better of saving your coins for a better gun or armor. You’ll hate yourself next week if something more valuable is available and you busted your ass this week and spent all your coins on the Hardlight.
That said, if you’re coin hunting, there are two available in the campaign, one as a mission reward for one of the Venus missions (can’t remember which one, but if you completed the campaign you already got it, you can’t miss it), and one available in a golden chest on Mars. If you have alternate characters that are high enough level to get to Mars but you never bothered with the golden chests, that might help you out.
If you start a new character from scratch, it will take you somewhere between six and ten hours to make it that far.
You can run strike playlists, strange coins can be rewards for those. You could run them for hours and not get any, or you could get a couple in a single strike from rewards and engrams. It’s probably faster than a new character if you only need two, but there are no guarantees.
They can also drop as random rewards for public events, or as part of the once-per-day reward package for the first public event you do. And if you haven’t done the Nightfall either, they can drop as rewards for that.
So if you only have one character, I’d do a public event first (if you haven’t already today), Nightfall if you haven’t already, and then I’d run strikes and hope for the best, but be prepared to run a lot. They never seem to show up when you need them.
edit: I think they can also drop as faction reward packages, so if you’re a few points away from leveling up your Vanguard rank or Dead Orbit or something, knock out a few bounties to get that reward too. Assassination bounties give you the most Vanguard/faction rank.