Does EDI(sold by diffuser express) make the diffusers for Vertex? The EDI FlexAir™ Disc Fine Bubble Diffuser Unit looks just like the Vertex diffuser except the main body is purple on the Vertex unit and gray on the EDI diffuser.

The specifications are very similar:

EDI 7"(measurement taken from the membrane diameter) Standard diffuser design flow is 0.5-2.5 SCFM with an overall diameter of 9" or 229mm using an EPDM membrane.

Vertex 9" diffuser ( measurement taken from the overall diameter) design flow is 0.5-2.0 CFM using an EPDM membrane.