Are you sure the whole harness is shot?
How important is it to you that it look like the original?
Are the male and female halves of the connector in good shape?
In this case you have the terminal box, the dash panel, the special connector to the powerhead, plus what's under the cowl, so quite a bit. Is there a generator involved?
Judging just from the pics, the nymarine harnesses look to be of good quality, but expensive.
Of course, if you just want to run it you could probably put the solenoid under the cowl, eliminate the junction box and special connector, and use a more recent control box including the electricals.