I don’t have any specific recommendations as most solid core CTs, even the cheap ones, work great. I do recommend that you use one of the solid core CTs that have been tested and calibrated and are supported in the tables, or that you send me a couple of others you intend to use so I can do same.
The solid core CTs in the tables are all 50A with about a 9mm hole. The one that I used to carry was the Echun ECOL-09 which is UL listed, had protection diodes, and a 3.5mm jack.
Two others in the tables are the HWCT-004 and DL-CT08CL2. I believe these two are actually made by the same unknown manufacturer in China. They look exactly the same (except for the printing) and appear to be alike electrically as well. The HWCT-004 is harder to find, but both are usually available on either Ebay or AliExpress. They are very inexpensive.
The reason I don’t carry them is they are not UL or CE compliant and the IoTaWatt ETL listing requires only UL recognized CTs be sold with it.
That said, I have used both and in fact have some HWCT-004 in service in my home. They come with short wire leads, so it’s necessary to add a longer cord with 3.5mm jack and recommended to add a TVS diode.