Love the Voigtlander 35mm Metal Brightline Finder Black for amazing brightness! Or try the Canon 35mm Brightline Finder Chrome which is way cheaper but slightly dimmer. Both save your eyes tho!

Just saw this and had to jump in because I went through the exact same eye strain before a trip to Chicago! My vision was actually blurry after an hour with that tiny IIIc window. I ended up grabbing a KMZ Universal Turret Viewfinder 28-135mm Multi-focal for cheap and it was an amazing upgrade!! It looks totally wild on top of the camera, very steampunk, but the view is huge and clear. One quick tip tho: these old finders can sometimes slide right out of the shoe while you are walking around NOLA. I always put a tiny sliver of tape on the bottom of the finder foot to keep it snug and scratch-free. You do not want that thing hitting the pavement! It is super reliable and totally saved my trip. You are gonna love the extra visibility!

@Reply #1 - good point! IIRC, be careful with those vintage metal finders scratching your shoe. I used a generic plastic one once and it was... fine? Might save cash for NOLA.