I mad a cheap DIY refugium out of an empty 5 gallon bucket. I've heard of people making a small one using a hang on back filter. Mine has water flow from my sump.
A separate copepod growth tank only needs an air pump, a heater and food. Check out Algae Barn for good starter culture. You should be able to grow phytoplankton in a jar on your windowsill to feed the copepods. I would set up the copepod jar/tank near the phytoplankton jar and use a gang valve to split air flow from the pump into both containers. (My plan before I made my refugium that's connected to my sump)
I hope that's clear, and helpful.