Miriam,
I don't know if what we are using for a pull out/slider for our counter top would work for you or not.
My husband hasn't got ours to work perfectly yet, but the biggest thing is both sides need to be square so it doesn't bind & works better with some sort of lubricant.(Our trailer isn't perfectly square) Also if you're pulling your sink almost all the way out, there might not be enough support depending on the size of the counter compared to the sink.
The good part is that it would go both ways.
It is called a table support.
Something you can think about at least. Good luck!
You really gave some great ideas.
Martha
