Hi!

When choosing the Spell Sniper Feat, the cantrips Booming Blade and Green Flame Blade are not available to choose from, although I do have access to the Sword Coast Adventurer's Guide materials via my DM.

Thanks,

You'll only have access to them (in the character builder) through characters that are in the campaign. This requires using the campaign invitation link to create your character.

Yeah, that's where I was building the character. When selecting classes, I have the ability to select any SCAG classes (in addition to all of the other stuff my DM has unlocked for me).

It might be because as part of casting booming/green-flame blade you make a melee weapon attack, not a spell attack and therefore it might not fulfill the 'attack roll'' requirement for Spell Sniper (though I think it should). I also remember reading a tweet by someone (I think Mike Mearls) that Spell Sniper + Booming Blade allows you to use it at 10-feet with a reach weapon, so I think this is a bug, rather than intentional. Probably because the spell has no spell attack modifier like the other spells that qualify for Spell Sniper.

In case there was any question, here's a tweet from Jeremy Crawford confirming Spell Sniper works with Green Flame Blade (and by extension, Booming Blade): https://twitter.com/JeremyECrawford/status/663511408269627392

And for good measure, here's one from Mike Mearls: https://twitter.com/mikemearls/status/693129817055588353

Thanks Adam!