If you're looking for another retracting tonneau, my Pace Edwards Bedlocker has kept me pretty happy for the last year or so I've had it. Its a little pricey as its the electric version, but the overall design seems robust. As far as I can tell from the instructions on the Frontier, it looks like it will work with the Utili-trac. While I can't speak to the non-motorized version directly, it does appear to be lockable. You mentioned your complaint about waterproofing but the reality is retractables generally aren't going to be as good at keeping water out as they tend to sit inside the bed somewhat. Mine keeps the rain out pretty well (some very light moisture at the tailgate when it rains), but trips to the car wash yield a pretty wet bed as the people washing it run the mitts over the cover and force large amounts of water through the edge. I've had both a Leer Fibeglass Tonneau and the BakFlip and both of them kept water out much better. The Fiberglass Tonneau never got water in at all.
If you are open to different types of tonneaus, we will need more information about what you want out of it and the uses for your truck. Each type have their pros and cons which may or may not be useful to you. In my case, the Fiberglass Tonneau came with my Titan. Looked great and made the truck look really beefy, but it was the least useful to me as most of the things I haul are taller than the bed. I thought about a lighter single piece cover, but after removing the cover once to haul a larger item, I realized I didn't have any place to put the cover when it was off. The BakFlip functioned great overall minus a few quality issues, but in the end, the fact that I couldn't see my motorcycles when hauling them made me too nervous. I lost a bit of bedspace with the retractable, but all of my M/C's will still fit with the tailgate down.
Here's my review of the PE Bedlocker:
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