Where can I get these nipple fittings?

[dochou]

Hello, I have a 20 year old geo calcium reactor. The tubing for the effluent and CO2 is old and hard, so Im replacing it. But the end of the tubing have small plastic fittings inside the tips so that they can be secured to the reactor fitting. I circled the unit put together on the reactor. They're really small and function to make the ends of the tubing rigid. Any help is appreciated.

 

[Srt4eric]

Change then to the push to connect though. Same thing.

John Guest 1/4 to 1/4 male adapter

 

[Galoot]

I agree with Eric. Dump the compression fittings go with push