Tumblr, I have a signal boost type thing for you!!
Recently I bought a binder from this brand of binders off of eBay, and I was rather happy with it! I know that binders can be very expensive, but bought off eBay these are pretty gosh darn cheap - about $8, including shipping!
I would recommend this for smaller to medium sized chested trans*/genderqueer individuals— I myself am a 34C and while it did not completely flatten my chest, it was a very sizeable difference and looked more like pectoral muscles than anything else, even in a tight t-shirt. I do not know how this binder would fit on chests larger than mine.
HOWEVER! One thing to be wary of— Though I did not buy from this seller in particular, I did buy from this same brand. So, just in case: This particular binder does not / may not come in discreet packaging. If your living situation is that where you are not “out” or would not be safe with a parent/guardian/roommate knowing (or at least avoiding awkward questions, the lattermost I know from experience) I do not recommend this product. It’s literally labeled “binder” and comes in semi-transparent packaging. Please be careful and protect yourself if this is risky for you!!
Otherwise, for small-to-medium on a tight budget looking for binding solutions, I would highly recommend this product! It comes in white, grey and black.
EDIT: I’m so glad for how many people have found this binder useful and cost efficient! I’ve gotten several messages asking about the particular listing I’ve linked, though, as the listing has ended. HOWEVER you can find it for similar/sometimes even lesser prices on eBay by searching “chest binder” as well as other various keywords such as “trans, lesbian, tomboy, ftm” et cetera. The sellers are usually from China.