I tried going the folding route last year for a long commute and it was kinda a disaster. I bought a cheap folder thinking it would save space but the hinge kept collapsing whenever i tried to type on my lap. If youre gonna be on a train for 48 hours, you really need something that wont buckle under pressure. I ended up getting the Logitech Keys-To-Go 2 Ultra-Slim Wireless Keyboard because it feels way more solid and reliable. It is usually under $80 too which fits your budget perfectly.

• super slim so it fits in a side pocket
• keys have a decent clicky feel
• battery lasts forever basically The iClever BK03 Foldable Bluetooth Keyboard looks neat but honestly the build quality of the logitech is worth the extra peace of mind for travel. Its one solid piece so you dont have to worry about mechanical parts failing while youre in the middle of nowhere.

I would suggest being very careful with anything that folds if you are writing for hours. Those split keys and weird hinges usually ruin your muscle memory. If you want something that actually fits in a backpack but feels solid, consider these:

• Arteck HB030B Slim Portable Wireless Bluetooth Keyboard has decent scissor keys and is super cheap.
• Microsoft Designer Compact Keyboard Bluetooth is incredibly thin and much more stable than a folder.

Building on the earlier suggestion about how folders can be a disaster, I've had similar issues. I remember packing a flimsy folder for a long trip to save space and the spacebar just... gave up halfway through. If you're on a budget and need it to survive 48 hours of heavy writing, I'd go with something more rigid.

• OMOTON Ultra-Slim Bluetooth Keyboard is super cheap and surprisingly tough. Its light enough to not notice in a bag but wont flex when you type on your lap.
• Logitech Pebble Keys 2 K380s is usually on sale for around forty bucks. Its round keys take a minute to get used to, but the build quality is much safer than any hinge design. Personally, I'd rather have something slightly thicker that I know is gonna work when I open my iPad. Being stuck with a dead keyboard on a train is the worst feeling... plus you'll save enough money with these to buy a few decent meals on the trip.

Honestly, the keyboard struggle is real. I feel your pain so much. Dealing with flimsy gear while trying to get actual work done on a train sounds like an absolute nightmare, and I have definitely been there with equipment that just fails mid-sentence. It is honestly so frustrating when you spend money on something portable that turns out to be total junk the second you need it to perform. Building on the earlier suggestion, if you really need something that can handle a marathon writing session without falling apart or feeling like a cheap toy, you might want to look at the Satechi Slim X1 Bluetooth Backlit Keyboard. It is built like a tank and fits into a backpack sleeve easily. Another solid bet is the Keychron K3 Ultra-slim Wireless Mechanical Keyboard, which gives you that real tactile feel without being a massive brick in your bag. Neither of these are foldables, so you wont have to stress about hinges snapping at the worst possible time. Good luck with the trip, hopefully you find something that lets you get your writing done in peace.