Chromatic Starramp$0.33Nearly identical fixing artifact that replaces itself, but it draws on sacrifice rather than immediately. It fills the same role in colorless and multicolor decks that want cheap mana fixing plus card flow.
Golden Eggramp$0.24A cheap artifact that fixes mana and replaces itself, serving the same smoothing role in slower decks. It is slightly more restrictive because it costs mana to sacrifice for the draw effect.
Mishra's Baubleutility$12.88Another 1-mana artifact that replaces itself and helps with deck smoothing and artifact count. It does not fix mana, but it is a close budget utility equivalent for cantrip artifact shells.
TerrarionrampBudget$0.12Very similar one-mana fixing artifact that draws a card after being sacrificed. It is slower to use because it costs two mana to activate, but it plays the same color-fixing role.
Claws of Gixutility$8.28Cheap colorless artifact that can be sacrificed for utility and card-neutral value. While it doesn't fix mana, it occupies a similar low-cost artifact slot in combo and sacrifice decks.
Wandering Fumaroleutility$0.27Not a direct artifact equivalent, but it is the kind of low-cost color-fixing utility that decks using Chromatic Sphere often want. It provides mana smoothing in a land slot rather than an artifact slot.
Arcum's AstrolaberampBudget$0.17A premium one-mana fixing cantrip artifact that often outperforms Chromatic Sphere in multicolor and snow-focused decks. It is banned in some formats, but functionally it is one of the closest upgrades.
Elsewhere FlaskrampBudget$0.12A low-cost artifact that helps smooth mana and can replace itself when it leaves the battlefield. It is slower and more awkward than Chromatic Sphere, but serves a similar fixing and cantrip purpose.