If you don't go dedicated, they become much more affordable and these have a good reputation. I'm thinking of getting one for my D500 to use at the ocean this coming summer (Nags Head), recording video and stills while out with the family in the waves and possibly getting some shots of the surfers.
Amazon.com : DiCAPac WP-S10 Pro DSLR Camera Series Waterproof Case : Underwater Camera Housings : Camera & PhotoAmazon.com : DiCAPac WP-S10 Pro DSLR Camera Series Waterproof Case : Underwater Camera Housings : Camera & Photowww.amazon.com
The above link is just an example and not picked for a specific camera body.
Oh! I bought one of these for my Leica M9 a couple of months ago after consulting their size/compatibility chart but I had to return it because:
(i) the size/compatibility chart didn't take into account the size of any lens,
(ii) it didn't take into account that you have to 'roll up' the opening to create the airtight feature,
(iii) while the accompanying photo appeared to include finger holes to allow for manual focusing, the one I had didn't have those finger holes and when I asked them about it, they said it's not really for manual focusing. It offered limited movement only.
I have considered trying a larger size or type.