Building on the earlier suggestion, do you actually need external recording or just a bigger screen? I'm satisfied with how the Feelworld F6 Plus 5.5 Inch 4K HDMI Monitor handles framing for much less.

honestly i had issues with the Atomos Ninja V 5 inch 4K HDMI Recording Monitor fan noise being way too loud for quiet ceremonies. unfortunately its overpriced if you dont actually need prores raw recording. the Portkeys PT6 5.2 Inch 600nit 10bit HDMI Monitor is much better for your budget. it covers 100 percent dci-p3 color gamut which is wild for the price. just grab that and save your cash...

Just catching up on this thread and wanted to chime in. Like someone mentioned earlier, you really gotta figure out if you actually need the external recording feature or just the visual help. In my experience shooting high-stakes events like weddings over the years, reliability is the one thing you cant compromise on. Honestly, if youre just monitoring the R6ii, I usually suggest the SmallHD Action 5 5.5 inch 2000 nit Monitor. Its built like a tank compared to the plastic budget stuff and the UI is much cleaner. The 2000 nits brightness is basically a lifesaver for outdoor ceremonies... trust me, squinting at a dim screen while the couple is doing their rings is a nightmare. I've tried many cheap brands and they often have color shift issues that make it hard to nail the white balance accurately. If you want something even bigger, the Desview R7II 7 Inch 2600nits Touch Screen Monitor is a solid alternative that fits your budget, though its a bit bulkier on top of an R6ii rig. Just a pro tip from a cautious shooter: dont forget to buy a high-quality cable like the Zilr 4K HDMI to Micro HDMI Cable 45cm. I've seen so many people buy a nice monitor then use a cheap cable that cuts out mid-shoot. Stick with something reliable so you can focus on the wedding instead of troubleshooting gear. Let me know if you need help with battery setups too!

bump

I have been shooting weddings for about six years now and honestly, the biggest mistake I made starting out was ignoring the weight and the cables. The R6ii is a beast, but those HDMI ports are kinda fragile tbh. I have seen people snap them mid-ceremony because they bought a heavy monitor and didnt use a cable clamp. Seriously, whatever brand you go with, please get a decent cage or at least a clamp... it wont be fun to deal with a repair bill right after the wedding. Also, dont get caught up in the cheapest is best trap just to save a few bucks. In my experience, some of those ultra-budget brands have terrible color shifts that make skin tones look super weird. Since its your sisters wedding, you really want to make sure the colors you see on the screen actually match what the camera is recording. I have wasted so much time in post trying to fix white balance because my monitor lied to me during the shoot. Just something to keep in mind tho.

^ This. Also, WanderingPoet is spot on about the cables. I had issues with my R6ii setup recently where the signal kept dropping because the micro-HDMI just doesnt seat right without help. It is honestly the most disappointing part of the camera design... such a pro body with a hobbyist port. If you want to stay under that $400 mark but still get something decent for a wedding, maybe look at the Osee T5+ 5.5 Inch 1000nits Daylight Viewable Monitor. Its way brighter than the PT6 and that 1000 nits makes a huge difference if you end up shooting the reception outdoors or near bright windows. Since you are looking at the DIY route to save money, grab a SmallRig EOS R6 Mark II Camera Cage and make sure you add the SmallRig HDMI and USB-C Cable Clamp. It is annoying to spend extra on bits of metal, but trust me, losing your feed while the bride is walking down the aisle is way worse than spending fifty bucks on a clamp. Just build the rig yourself and you wont have to worry about the port snapping.