Yes, 50/50 e-liquids are available in some short fills, however they are not as commonly found as high VG short fills. This is because 10 ml bottles can contain nicotine, allowing for a variety of nicotine strength options, whereas short fills must be sold without nicotine.
While short fills leave room for the addition of nicotine, they are designed to be mixed with enough nicotine to create a 3 mg/ml e-liquid. 10 ml e-liquid bottles can have strengths ranging up to 20 mg/ml, allowing for those who were smokers to effectively match their previous nicotine intake.