Need a Water hose under the Sink Slide out?

You are probably right about the 3/8 hose, I though I could find the 1/2" like the one that came out, but so far no luck. I do know that there are several of the hoses, some on the Hydra hot, they are the same fittings and hose just shorter.
I did go to a pluming supplier and he was no help either, all stock the same size hoses, I even went to a place that make hoses, and they did not have the correct fittings or some excuse.
I did not want to use hose clamps like a shade tree mechanic.
What would be the best RV supply house in this Area, Anyone?

First off are you sure that the hose is half inch? I would suggest contacting a plumbing supply house to see if they can help you out. I would also suggest getting a stainless steel braided hose for the replacement. The 3/8" line you found will give you enough water to do what you need it to do. For a plumbing supply house I think that there is probably a Furguson Plumbing Supply in your area. They were always helpful to me when I was plumbing. Good luck.
Ron
Another thing that you could do is use Sharkbite fittings and PEX pipe and make your own hose.
Ron

A 3/8" hose to supply the sink will be more than adequate.