+1 on Dylandog's advice.
On a tight budget, aim for narrow and long, instead of broad and short. 40 X 150 mm (1"3/4 X 6") is a good size. You need a bit of distance to perform a good honing stroke. At the same time, there are many razors that don't lay perfectly flat on a broad hone, whether that's due to a smiling curved edge or a slight warp in the blade. Such razors are a bit easier to hone on a narrow hone.
Many vintage coticule razor hones were 35 X 150.

Bart.