There are some GREAT 3/4 options and full size options out there.
The Jupiter JTU1010 is a 3/4 4 valve tuba and it's pretty solid. Jupiter horns are better than many people think.
Conn makes the 5JW series, and they're pretty solid and not too huge. King also has the 2341W as a front-valve tuba. Both of these are full size tubas.
Most anything else will either be close to $10k each (Mirafone) or may/will be junk (Allora, Eastman).