Amazon.com: NC Tapered Steerer Tube Conversion 1 1/8 Inch to 1 1/2 Inch Crown Racing Ring Fork Adapter, Straight Tube Fork Repairs The Bottom Ring Resistance 1 1/8 Turn 1 1/2 : Sports & Outdoors
1-1/4" to 1-1/8" Headtube Headset Reducer / Adapter 1.25" to 1.125"
New headset allows use of tapered steerers in some 1-1/8in head tubes - BikeRadar
BOX Two Headset Adapters (1-1/8" to 1") | Time 2 Shine BMX