When my yamaha 703 tilt and trim switch stopped working I rigged up a separate toggle switch and mounted that on the console.
Stainless steel waterproof (on) off (on) toggle switch.
Wiring on mine was already there as I believe the wiring loom already has spare connections in place as well as the connections to the 703 switch. Three wires, from memory, Blue (up) green (down) other not sure but central position on switch.
The switch on the console can then be placed any side, to what ever thumb you like
I like it better now as it's a straight forward up and down movement.
Also having rigged that up and working, I then had the courage to try and mend the original switch on the 703 handle. To take it all apart involves much hassle and I was reluctant to separate the two halves. Long story short, I just carefully pulled the rocker switch out from the handle in situ, but damaged the plastic waterproof membrane covering, cleaned the switch contacts and bingo it worked again. Gently manipulated switch back in to position and it's been ok now for two years and counting. So now have two switches in case the other stops working.