Mind Stoneramp$0.31A classic 2-mana colorless rock that ramps from two to three mana, serving a similar early acceleration role. It also has a late-game sacrifice mode for card draw.
Thought Vesselramp$1.92Produces one colorless mana and carries no maximum hand size, making it a staple utility mana rock. It fills the same colorless ramp slot with an extra upside.
Sky Diamondramp$0.19A cheap artifact mana source that helps bridge into higher-cost spells, similar to how Ur-Golem's Eye accelerates mana. It is slower on output but much easier to deploy.
Coldsteel Heartramp$0.99Another two-mana rock that fixes or ramps and is commonly used as efficient colorless acceleration. It provides comparable utility in a more efficient package.
Everflowing Chaliceramp$0.19A scalable mana rock that can eventually produce multiple colorless mana like Ur-Golem's Eye. It is more flexible and can be stronger in the late game.
Hedron Archiveramp$0.25A colorless artifact that taps for two mana, closely matching Ur-Golem's Eye's output. It costs the same and adds a valuable card-draw sacrifice mode.
Worn Powerstoneramp$0.36This three-mana rock enters tapped but produces {C}{C}, making it a very close functional analog. It is often preferred because it comes down a turn earlier.
Dreamstone Hedronramp$0.19A larger artifact mana rock that produces three colorless mana, occupying the same high-end ramp slot. It is slower to cast but offers a similar big-mana role with upside.