Actually, no one makes PE for this kit yet...only some white metal fittings from HR and John Brown...if you want radars, you either have to wait for the upcoming Tom's Modelworks PE set, or scratchbuild...
When I did my SC-5 Air Search radar, I actually used a model railroad building window frame, covered with wire mesh, and added some dipoles made from brass wire. Not perfect, but it looked very convincing from a foot away.
With regards to the Mk 4 radar for the MK 37 Fire Control Director, wire mesh bent into a W shape profile will suit your needs. The kit's support arms can still be used. Here's a pic to show you what I'm talking about.
and a photo of the Lavellette's Mk 37:
And here's the drawing for the SC-5 radar:
Hope this helps.
Jeff