Surfing Waves

So I recently came across a used board with ports for 3 fins. 1 of the fins is missing/broken, so I took off another unbroken fin and currently use the board with only 1 fin. I'd like to get it back on 3 fins, but the connectors are round and I can't seem to find anything like this... Please take a look at the photos below and let me know if you've seen anything like this and know where I might find replacements.

No one...? Really...?

Ok I'll try to help, put a picture of the board up preferably showing the brand name.
I guessing the board may be a soft top in which case the fins may well be unique to the brand and that is why no-one knows( I certainly don't) If a brand is evident you could try Googling that brand and see for yourself!

I've never seen it before, it might be custom to that board or something that has become obsolete. You should just pay to have FCS plugs put in for the one you are missing, or replace all three

Nope, I've never seen anything like this before.