cumquat

first i'll give you a tip, waterproof should not be a requirement. reason? you can achieve the same (or even better) results with a tube of silicone glue (a common name brand is shoo goo). just apply a bead around all seams and fill any openings.

now a question, is RTR mandatory or are you willing to look at kits? if a kit is acceptable you will have a few more options. i'll save recommendations until you answer so i dont fill up the page with models you have zero interest in.