Since you've already used your transducer, the free exchange option from Humminbird is no longer an option. You can just buy their excellent flush-mount through hull xducer for about $35, though. That is what I used on my 'yak. Yes, you have to drill a two-inch hole in the hull. But with the rubber washers included and a bead of goop, it'll never leak.
I have the same fishfinder, and my setup is outstanding. Perfect readings of depth, structure, and fish. However, my replacement transducer doesn't have the temp sensor. I carry a simple digital thermometer that I drop into a scupper to make up for it.
Outside view, installed. Note that it protrudes from the hull only 0.20" and is flat.
Here's what it looks like from inside...
