You can farm for shards in an extremely round-about way, much more easily if you've unlocked an exotic sword, as upgrading them costs no resources outside of either XP or Motes of LIght. Buy an exotic weapon from the exotic weapon kiosk. This will cost you 1 exotic shard and 2500 glimmer. Level the weapon up fully while activating all nodes (thus why it's better for the exotic swords as they don't cost things like helium filaments, etc.). Once you have activated all the nodes (not just unlocked them but actually activated them) dismantle it for 2 exotic shards. It's not as easy as just popping a Three of Coins and hoping RNG kicks in or opening raid chests for them, but it's a lot less time consuming. You end up just needing to farm for glimmer and motes of light, both of which can be gotten relatively easily at this point (with most people having a large amount of motes saved up), so this method might be your best bet if you just want shards when Xur isn't here. Otherwise, you need to farm for Strange Coins, which are still up to RNG for things. Glimmer and motes can be farmed with certainty (and extra motes from RNG) so it's really up to you.