I went ahead and got a replacement from
3kawitriples@gmail.com, Danny
It's a hairline crack, drops coming through, just below the sight glass. Finally found out it was a microscopic crack. I could have tried some sort of glue/cement, but this already drove me crazy for too long.
Even if I repaired it, it could just continue cracking I guess.
Other solution would have been perhaps using a kreem coating like we do on metal gas tanks(?)but it's not cheap, and what if it started clogging the lines?
I now plan on mounting the new tank with rubber washers or o-rings to isolate vibration.
Took 44 years to crack I guess