Your money so buy new if you want. Personally I'd find a used one. 30-50 year old PTO spreaders in good condition (some near new) can still be had around here if you are patient. Usually under 4K too. Anyone who bought them new and only seasonally used them "once a year to clean the piles up" and cleaned and oiled them and put them away they are still solid.
I still run a older small PTO box spreader and it's "big enough" for several days a year I use it.