you're talking about the bow navigation light, and he's asking about the anchor light on top of the mast
My anchor light uses a Festoon 43 bulb on my 90 Pearson, but beware....don't get one so bright it attracts every bug in the anchorage if you do anchor out, as it's quite a mess in the morning. My 1st one was 62 LEDs, and I've bought a 36 to replace it with this season. Being LED, it will still be more than bright enough.
You're right though about the nav light, they don't make them anymore. I found the last 2 that I could find in the world in England 5 years or so ago and had them delivered to me through Germany, USA and then to Canada with the help of other boaters on the net!