Dragonlord's ServantrampBudget$0.25This is the closest functional analogue: it reduces the cost of your Dragon spells by the same amount, but on a cheaper body. It is also a staple in Dragon tribal decks across many formats.
Urza's Incubatorramp$17.46A stronger tribal cost reducer that can name Dragons and cut their cost by two. It is colorless, so it fits into any Dragon deck regardless of color identity.
Herald's Hornutility$4.65Not a direct reducer, but it provides ongoing tribal cost reduction and card advantage for Dragon decks. It is a common budget alternative for tribal consistency.
Cloud Keyramp$2.83A flexible cost reducer that can name creature spells or Dragons if you are in a tribal build. It is less specialized, but performs a similar mana-smoothing role.
Semblance Anvilramp$6.55Can reduce the cost of Dragon spells significantly if imprinted with a suitable card type, though it is more setup-dependent. In decks built to exploit it, it can be stronger than Dragonspeaker Shaman.
Morophon, the Boundlessramp$6.50In tribal Dragon shells, Morophon can reduce Dragon spell costs by one generic mana and also fixes colors. It is a much bigger engine piece for multicolor tribal decks.
Hazoret's Monumentramp$3.20If your Dragon deck also has red creature-casting density, it can reduce the cost of your red creatures and provide extra card filtering. It is not as narrow, but it offers similar mana efficiency.
Brought Backutility$2.00Not a cost reducer and not a functional equivalent.