I have a Philips (Magnavox) D2999 multiband radio that has a somewhat peculiar external antenna connector. It resembles a BNC but that type connector doesn't seem to fit. What is it and where can I purchase one? I miss listening to hams on 20 and 40 meters.

a picture would help? does it look like sma connector like on a baofang uv 5r? only tiny er

This ad mentions a “KOK” plug, which I have never heard of:

https://www.universal-radio.com/catalog/portable/d2999.html

jr

Possibly one of these PAL adapters will fit:

https://www.amazon.com/s?k=pal+antenna+adapter&ref=nb_sb_noss_2

.

KOK1 Plug.

That photo is of a Belling and Lee type aerial connector that's commonplace for TV aerials in the UK.
https://en.wikipedia.org/wiki/Belling-Lee_connector

https://www.universal-radio.com/catalog/parts/kokconn.html

I always kept a pair of adaptors for those antenna connectors in my assortment of stuff as most of the multi-standard VCRs that used to cross my bench had them. Not knowing the exact name until now, I called them "Euro antenna connectors". Probably bought them from MCM back in the day.