Been thinking about your budget for a bit and figured I would weigh in from a gear nerd perspective. Over the years I have spent way too much time tracking price drops on the Sony Alpha line, specifically for models like the a6400 and the ZV-E10. If you are trying to stay under 600, you really need to be surgical about it. Honestly, those browser extensions are okay but they usually just scrape expired codes that everyone already knows about. Basically, you are gonna want to trigger the eBay algorithm manually. In my experience, this is the most reliable workflow for snagging a deal when you are on a tight deadline:

• Set a Saved Search for Sony Alpha Refurbished and filter by Buy It Now with a hard price cap of 580.
• Add the specific unit to your Watchlist. Sellers often send private 5 to 10 percent discount offers within 24 hours just to move inventory.
• Check the specific seller store page directly. High-volume refurbishers often have a store newsletter that gives a one-time code upon joining. Ngl, the real secret is the seller-initiated offers. I managed to get an a6100 for a steal just by letting it sit in my cart for two days. Since you are on a timeline for next week, pay attention to the shipping location because some refurb houses are slow. Tbh, a refurbished unit with 425 phase-detect AF points is what you want for travel shots, so aim for the a6400 over the older a6000 series if you can find the right coupon... its worth the extra effort for that focus tracking and the 4K internal recording.

Honestly, I get so hyped talking about this because I saved almost 150 bucks on my current setup by being a bit obsessed! Last summer, I was in your exact shoes trying to snag a refurbished unit for a photography workshop. I tried those weird 2 dollar coupons you see for sale... big mistake! Most of them are totally expired or just fake, so please dont waste your money on those. It was a total disaster and I felt so silly afterwards. Here is what actually worked for me after a lot of trial and error:

• Newsletter signups are legit gold! I signed up for the official refurbished emails and got a 15% off code within like 20 minutes. It was so easy!
• Check the top banner of the specific refurbished landing page because they usually run category-wide sales for 15-20% off every single month. This is how I scored the one I got.
• Honey is okay, but it rarely catches the high-value refurbished codes that are specific to certain sellers or brands. I ended up getting my current setup for way under my budget by just waiting for that specific newsletter blast. It felt amazing when the code actually worked at checkout! Ngl, the adrenaline of seeing that price drop right before a trip is the best feeling ever. Just stay away from those sketchy sellers selling codes, its basically a coin toss and usually ends in a headache. Stick to the official promos and you'll find something fantastic for your trip!

Omg you're gonna have such a blast with a Sony! Seriously, their autofocus is absolute magic for travel shots!! Since you're looking for a refurbished unit under 600, you HAVE to check the specific eBay Refurbished landing page directly instead of just searching the main bar. They run these insane sitewide promos like every other month where you get an extra 15% or 20% off certified refurbished gear using a specific code like SHOPREFURB or similar. It's way more reliable than those browser extensions that usually just spin and fail at checkout tbh. One super pro tip that works for me almost every time: add the camera you want to your Watchlist and just let it sit there for 24 hours. Sellers get a notification and they'll often send you a private discount offer directly to your inbox! I've seen them drop the price by 5 to 10 percent just to close the deal quickly. Since you're on a deadline for next week, this is definitely your best bet for a fast discount. Look for sellers like Secondipity or Adorama's eBay store because they are official partners and those refurb codes actually work on their listings. If you can snag an A6400 or even a ZV-E10 for under that cap, you're golden! Feel free to ask if you need help comparing specific models too, I'm obsessed with this stuff!