I actually ordered some bare PCBs here:
https://www.atlhifi.com/shop/bare-pcb/pcb-for-cmf-emi-rfi-filter/ and was sent a PDF document with several parts lists for different builds. There is also a ready assembled version:
https://www.atlhifi.com/shop/assembled-pcbs/emi-rfi-common-mode-filter-assembled-and-tested-pcb/
However, presumably due to the pandemic, the actual boards took ages to arrive, so as the circuit is so simple I decided not to wait for them and instead build them with prototype board (bodge board).
You can see the circuit diagram on the web site, but I don't think it would be right for me to share the details and parts list here.
The case is from Hi-Fi2000:
https://modushop.biz/site/index.php?route=product/category&path=260