This is bit unclear. Are you looking for an SD card reader that has a USB-C cable ... or a USB-A to USB-C adapter to use with an existing SD card reader that has a USB-A cable?
Most SD card readers that I know of still come with USB-A cables. If you need a USB-A to USB-C adapter, there are many ... I prefer short adapter cables like these from OWC or monoprice.com or even the Apple USB-C to USB-A adapter. They are less prone to disconnecting than simple plug adapters.
The Lexar Professional Workflow Dual-Slot UHS-II SD Card Reader comes with both a USB-C cable and a USB-C to USB-A adapter ... but even it sells for around £40.
I have an old Sony MRW-EA7 multi-card reader that has worked with every Mac I have owned in the past 15 years, and still works today even with a USB-A to USB-C adapter cable. A comparable reader today would be a Transcend RDF9 or IOGear Superspeed USB 3 multi-card reader. But both require an adapter cable.