Hey, I totally get the panic before a big shoot. I have been running the a7R V for a few months now and honestly, you dont need to drop $700 to get something that just works. I settled on a setup that cost me way less and it has been rock solid for my real estate stuff. Basically, that flicker usually happens when the monitor cant handle the handshake with the Sonys HDMI output at 4K. I have been super happy with the OSEE T5+ 5.5 Inch 1000nits On-Camera Monitor. It is light as a feather which is perfect for your gimbal setup, and the software is actually surprisingly good. Reminds me a lot of the high-end SmallHD stuff but for like a third of the price.

• Focus tools: The peaking is sharp. If your eyes are struggling, you can customize the peaking color and sensitivity to really make those edges pop.
• Reliability: I have filmed long walkthroughs in the sun and it didnt even get warm.
• Cost: Its cheap enough that if you drop it on a job, it wont ruin your month. If you find yourself shooting near bright windows (classic real estate struggle), check out the FeelWorld LUT5 5.5 Inch 3000nit Ultra Bright Monitor. It is blindingly bright so you wont need a sunhood, which makes balancing the gimbal way easier. Most flickering issues are actually just bad cables tho, so maybe grab a Kondor Blue High Speed 4K HDMI Braided Cable just to be safe. Good luck with the Chicago shoot!

^ This. Also, been using the SmallHD Action 5 5-inch 1000-nit Monitor for months and I am very satisfied with the stability. It handles the high-res signal from the a7R V without any flicker or lag issues. Technically, the UI is much cleaner than the cheaper brands, and it stays cool during long shoots. Dont forget that the cable matters just as much as the screen for reliability. I use the Zilr 4K HDMI High-Speed Cable 17.7-inch and it works well for gimbal clearance without stressing the ports. TL;DR: The Action 5 is well under your budget and works flawlessly with the Sony signal. Save the extra cash for some extra Sony NP-F970 Rechargeable Battery Pack units and you are good to go.

I've been shooting with that exact body for a while now. Those flicker issues are usually just old firmware... ignore the noise. Here is what I actually use:

• PortKeys LH5P II 5.5-inch 2200nit Touchscreen Monitor is great for gimbals since it's light and bright.
• Atomos Ninja 5.2-inch 4K60p HDR Monitor is the updated version that fixed most of those early V+ bugs. Both are rock solid and wont fail you on a shoot.