big, huge, large
a large grain surplus

small
projected
a projected surplus of $5.6 trillion over ten years

agricultural
budget, current-account, federal, social-security (AmE), trade
consumer, producer (both economics)

have, run (esp. AmE)
Japan runs a large current-account surplus.

generate, produce
project (esp. AmE)

cash, stock

in surplus
The pension fund is in surplus.

Surplus is used with these nouns:
energy, fund, inventory, stock