vinyl 1/2in tubing for supply to faucet
I suppose you might be able to find one fitting do this connection, but it's going to be much easier to use two that are very common at home stores.  First, you will need a 3/8" compression to 1/4" MIP (male pipe thread) adapter and then a 1/4" FIP (female pipe) to 1/4" barb (or whatever size you need) adapter.

These two adapters will connect with the common pipe threads (with teflon tape) and provide the barb you need on one side, and the compression fitting needed for the faucet.



Barb fitting



Compression fitting