Hey there, I honestly think you should just go with the official Canon BG-E20 Battery Grip for EOS 5D Mark IV. I was in the same boat when I first started out and tried a cheaper Neewer Vertical Battery Grip for Canon 5D Mark IV to save some money, but it just didnt feel right. It had this slight creak whenever I gripped it tight during vertical shots, and it made me really nervous about it failing or potentially damaging the mount. Since you mentioned shooting outdoors in unpredictable conditions, I wouldnt even look at third-party stuff. The Canon grip is built with the same weather-sealing gaskets as the camera body itself, which is huge for peace of mind. I have heard horror stories about moisture getting into the battery compartment of knock-off grips and frying the internals of the camera, and with an expensive body like yours, its just not worth the risk. One quick tip for you: if you get the grip, make sure you are using official Canon LP-E6NH Lithium-Ion Battery packs inside it. I noticed that when I used off-brand batteries, the camera would sometimes glitch or give me a fake empty battery warning on the screen because the communication between the grip and the body isnt perfect. Stick to the official stuff for weddings, honestly. Its way better to pay more now than to have your camera die or short out in the middle of a ceremony because of a cheap connection. It just feels way more solid and matches the 5D texture perfectly too.

Tbh, if you are really looking to save some cash but still want a grip that feels decent, I would look into the Meike MK-5D4 Pro Battery Grip for Canon 5D Mark IV. It usually comes with a wireless remote too which is a nice little bonus for long exposures or group shots. Its definitely more plastic-y than the Canon version, but for a wedding backup or a tighter budget, it holds up okay in most situations. Another way to save is to look for the official grip used. You can often snag a Canon BG-E20 Battery Grip for EOS 5D Mark IV from reputable used gear sites for like half the retail price. If you go third-party, just make sure you use solid batteries. I usually grab the Wasabi Power Battery 2-Pack for Canon LP-E6NH because they are reliable and way cheaper than the Canon branded ones. It makes the whole setup much more affordable for a working pro.

If the official price tag is a bit much, the Vello BG-C14 Battery Grip for Canon 5D Mark IV is the sweet spot. It actually has some basic weather gaskets and the buttons feel much more tactile than the super cheap alternatives. Its about $90 and fits the 5D body perfectly without that annoying wiggle some third-party grips have. Definitely a solid backup for long wedding shoots.

You absolutely have to be cautious about the electrical contact tolerances on those third-party units! If the communication pins arent perfectly aligned you risk a massive short circuit on the cameras main logic board which is a total disaster to repair. I always verify the signal continuity because the power delivery systems in these bodies are incredibly sensitive to even minor voltage fluctuations! I get so worked up over technical precision like that. It actually reminds me of when I was troubleshooting my home theater setup last weekend. I spent hours testing the impedance on every single speaker wire just to make sure I wasnt getting any signal degradation from the old copper. I ended up rewiring the whole living room just for peace of mind! It was a total rush once I got it all calibrated perfectly. Anyway... definitely keep an eye on those pins if you go the cheap route.