Omg congrats on the Seattle wedding gig!! That sounds so exciting but also super nerve-wracking lol. Ngl im always terrified of my gear failing during a big shoot so I totally get being cautious about what you buy. I actually grabbed a grip recently because I was scared of running out of juice mid-action and it has been a total lifesaver!! Here is what I recommend for staying safe:

• Honestly the Canon BG-E20 Battery Grip for EOS 5D Mark IV is the absolute safest bet! I found a used one for $110 and the weather sealing is incredible for that Seattle rain. Plus the shutter button feels just like the camera body.
• If you want brand new and under budget, the Vello BG-C14 Battery Grip for Canon 5D Mark IV is fantastic! It feels super solid and reliable compared to the really cheap brands. Definitely dont risk those $30 no-name ones tho... im way too scared of frying my electronics to try those!! Good luck with the shoot!

Just saw this and figured Id weigh in on the cost vs performance side. Since youre heading to Seattle, weather sealing is a big deal. Most third-party brands skip the gaskets to keep costs down.

• Canon BG-E20 Battery Grip for EOS 5D Mark IV: Only one I actually trust in the rain. Usually $130 used. Best button feel and real sealing. Pros: Perfect build. Cons: Pricey.
• Vello BG-C14 Battery Grip for Canon 5D Mark IV: Good middle ground at $90. Shutter feels okay but the sealing isnt nearly as robust as Canon. Pros: Affordable. Cons: Build quality is lighter.
• Neewer NW-5D Mark IV Battery Grip: Cheapest option. Good for battery life but the buttons feel cheap and I wouldnt trust the seals. Pros: Very cheap. Cons: Mushy feel. For a paid wedding, Id probably just hunt for a used Canon one. Better safe than sorry when the clouds open up.

Saw this earlier but just now responding! I totally get wanting to save some cash because gear is so expensive! I was in the same boat last year for a rainy outdoor shoot and was terrified about my 5D IV getting soaked. I ended up grabbing the Neewer Battery Grip for Canon 5D Mark IV and it was honestly such a game changer for me! People always say you have to buy the original brand but this thing has been amazing for my workflow and hasnt let me down once. Here is why I think it is a solid choice:

• It fits super snug with zero wiggle which is a huge deal for me
• The shutter button has a really nice clicky feel not mushy at all
• It handles my Canon LP-E6N Lithium-Ion Battery pairs perfectly without any weird error codes I have dropped my bag a couple times (oops!) and it held up like a champ. For way under your budget it leaves so much more room for extra memory cards or even a nice dinner after your Seattle gig! You are gonna love having that extra grip space for vertical shots... it makes those long wedding days so much easier on the wrists tho!

Im not sure about third-party grips for weddings. Iirc my old one leaked during a storm once.

• mushy buttons
• bad seals Basically ruined the shoot tho...