Hose is available from eTrailer as well as many RV stores. I have never seen a proper 1/2 PEX to 1/2 hose adapter. Just because the RV industry clamps hose to a PEX fitting does not make it right. You need a hose barb that is larger and a different shape to connect hose. I find it funny that they say that an RV is tested to a certain water pressure while containing these mismatched components. A fitting that might work for you is
this one, although still not correct. A hose should be connected to a barb such as
this.