You can buy them here, all types in stock. You probably only need the silver.

www.kitepower.com.au/collections/other/GoPro

You can buy them at the CONTOUR shop

Seriously, do a google for "gopro fogging" and check out the nightmare it is to fix that problem. My GoPro gave the ****s once too often so I got a Contour Roam 2 (waterproof to a meter or so) and as it doesn't need a case - it doesn't fog. Ever. IQ is as good as it needs to be, if you're not a computer whiz or photographer and not interested in the 4K twaddle.

I would just get the white for your first one ..jb hifi do them for $258.Get an orange floaty as well to stick to the back of it and make a leash out of kite line.There would be nothing worse than getting the black and then loosing it in the surf.

The softwear editing program from GoPro (cineform) will handle the compression and allow you to edit the footage on most up to date computers, even using 4k. Any MAC computer than runs Final Cut Pro will handle the job, I edit 4k on my Mac book Pro and my IMac no problems.

But as you say no real need to shoot in 4k, even 720p upscaled thru FCP is going to do the job, anything uploaded to the web is only 720 or at best 1080 on Vimeo.

The Wifi controller is handy for saving battery and editing time, use the wifi to just shoot the bits you want, turn it on when you are doing a trick or riding a wave and then turn it off while you are just cursing, cuts out all the boring bits. saves battery, card space and editing time.

IMO it helps with the fogging issue, the camera runs quite hot is continually left on and hence it can produce fogging. Turning the camera on and off doesn't seem to produce the heat/fogging issue. Ive just returned from 3 weeks in the cook islands where we used the Black every day and didn't experience the fogging issue once.

I have also read that sealing the camera in cooler conditions, i:e at night and not opening the case during the hotter parts of the day helps, not sure how true that is but....

Ha, it will all make sense when you get a GoPro, my advice get the best you can afford.