I haven't checked the dimensions of the 1020 but here is a water resistant one by Ibera.
Amazon.com: Ibera Bicycle Weather Resistant iPhone 4, iPhone 5, Smartphone Case: Sports & Outdoors
That case is actually too small for the 1020. The one thing I did notice in the description was it said it wasn't for rough riding. This might work for road cycling, but I wouldn't take it on a mountain bike trail. I found one on the manufacture's site that has the dimensions listed as larger than the 1020's dimensions. 5 inch Smartphone Case 5 with Bike Mount IB-PB16 | IBERA ? The Cycling Life
Here it is on Amazon
Amazon.com: Ibera Bicycle Waterproof Smartphone Case, 6" screen (Samsung Galaxy S III, Galaxy S4, HTC One): Sports & Outdoors
The PRO mount is strong yet light-weight and fits handlebars with a diameter between 19mm - 35mm.
You will require a minimum clear space of 42mm on your handlebars to secure.
Twin anodized screws fix the mount to your handlebars, providing a stable base for the case.
Includes two liners to cushion against vibration and protect your handlebars.
...
Fits phones no larger than 138mm x 75mm x 15mm