Amazon.com: FangKingNo10pcs 3/4" White PVC Pipe Coupling Adapter Pipe Fittings (Slip to Slip) Schedule 40 Easy to Install,and High Tensile for Home or Industrial Use (1 Pack of 10pcs) (0.75 Inch) :
Charlotte Pipe 4 in. PVC Schedule 40 MPT x S Male Adapter PVC 02109 2000 - The Home Depot
NDS PVC Adapter, 4 in. DWV/SCH40 Hub X S&D Hub 3P16 - The Home Depot
Charlotte Pipe 1-1/4 In. Sch. 40 PVC Coupling - Gillman Home Center