I have the Underworks 983 Triptop binder in XS and it's too big.
It still binds, but not as well as I'd like and it's really easy to get on and off. It also puckers quite a bit at the front and bottom. It's definitely too big.
If I recall correctly, my true size was about 28".

Are there any good binders that come in smaller sizes?

Thanks

T-kingdom has binders in smaller sizes.  Their smallest looks to be a 28-30" size, but apparently they also run small.  I've never personally tried 'em, though, so I can't recommend what style to get.

I recommend t-kingdom as well

yeah I heard that t-kingdom binders can be pretty small

Fantastic.

Now just to overcome the problem that I'm poor.

haha yeah I have the same problem I need money for a binder.