Forget the shimano hub ! You require a freewheel with a lot of engagment points. It depends of your willing too. If you want to ride a single speed bike (the best solution for trial according to me) or not ! If you are single speed addicted you can ride an DMR revolver hub with a Try all 108.9, Tensile, Monty or Eno freewheel. Else a Chris King, DT Swiss or a Hope pro trial are good alternatives. Atomlab produces this kind of hubs too. Concerning the rims, a lot of trial rims are available: Echo, Try all, Viz!, Sunn/Un (only available in France), Onza. They are very wide (between 38 milimeters to 47) to be easy balance on your bike.