One of my 2 binders (Underworks tri-top) got too loose and can't bind well anymore.
Ok, I still have the other but I need at least 2 to rotate them or I'll destroy the other one soon. I wear them daily.

Do you know if I can do something to make it compress more? I thought about resizing the sides... but if you have ideas please share them with me. I am not very skilled in sewing but I can learn...

I ask because I can't afford a new binder, so I want to try to fix the old one 

Thank you

Do you have a sewing machine? I don't see any reason why you couldn't just cut it up the sides, take off an inch or so, and then reattach it, but I'm not sure you could sew it securely enough by hand.

I took doubled over thread, a looooong piece, and sewed my binder up the sides to make it smaller. If you do slightly bigger stitches and overlap them a lot, it seems to hold well and allows a tiny bit of stretch/give.

I took it in an inch on each side. Then I wear it inside out, so the sticking out seams are on the inside.

Thank you guys, you helped me a lot.
Unfortunately I don't have a sewing machine so I'll try to do it by hand.
I fear that cut and stitch back by hand wouldn't hold strong enough, I'll try to fold/overlap a little the sides and sew them.

I put mine in the dryer after I wash it so that it shrinks. Works well enough for me. I have 2 binders as well (tritops).

I also have a binder that got really loose, but I just resized the sides. It worked for some time, but as I used the binder the sewing went up and I had to sew it again. But it's definitely cheaper than buying a new binder