I was looking though the spell lists and noticed that (as far as I could tell) there are no ranged variants to improving ranged attacks like the melee spell attack spells do for melee attacks (e.g. booming blade, green-flame blade).

What I am talking about are the spells that stats:

As part of the action used to cast this spell, you must make a melee attack with a weapon

Are there any ranged variants of this? Spell of any level would be acceptable.

I am not looking for identical language, just spells that enhance a "normal" ranged weapon attack.

There are are several!

While the booming blade and greenflame blade cantrips are the most obvious spell-assisted melee weapon attack options, that type of enhancement isn't limited to melee attacks. The spells listed below revolve around ranged-only. There are some other spells that apply to both, but I've focused this on the ones that require ranged.

The following are some examples, but others exist if you look at the spell descriptions in the various source books.

Cantrip

Magic Stone(Elemental Evil, 160) is the most obvious option here.

You touch one to three pebbles and imbue them with magic. You or someone else can make a ranged spell attack with one of the pebbles by throwing it or hurling it with a sling. If thrown, it has a range of 60 feet. If someone else attacks with the pebble, that attacker adds your spellcasting ability modifier, not the attacker’s, to the attack roll. On a hit, the target takes bludgeoning damage equal to 1d6 + your spellcasting ability modifier. Hit or miss, the spell then ends on the stone.

Levelled Spells

If you utilize your spell slots, you've got some other options. The Ranger spell list contains a lot of examples:

Lighting Arrow(PHB, 255)

The next time you make a ranged weapon attack during the spell’s duration, the weapon’s ammunition, or the weapon itself if it’s a thrown weapon, transforms into a bolt of lightning. Make the attack roll as normal. The target takes 4d8 lightning damage on a hit, or half as much damage on a miss, instead of the weapon’s normal damage.

Flame Arrows(Elemental Evil, 156)

You touch a quiver containing arrows or bolts. When a target is hit by a ranged weapon attack using a piece of ammunition drawn from the quiver, the target takes an extra 1d6 fire damage. The spell’s magic ends on the piece of ammunition when it hits or misses, and the spell ends when twelve pieces of ammunition have been drawn from the quiver.

Two Paladin Smite Spells do not exclude ranged attacks

Branding Smite and Banishing Smite both state that

The next time you hit a creature with a weapon attack before this spell ends

As opposed to other smites that require a melee attack these do not exclude ranged attacks.