If you have a little room for a 10G tank
I would highly recommend to DIY a 10G sump
I did it myself, and is super easy and simple
Used 10G tank, $5, new for $9.99
Plastic board, glue, $5~15
Used good condition pump, $15
Plastic soft pipes, connectors, switches, $10~20
And drill 2 holes on the intake of the Refugium sump,(in case power out, water will only fall to where the level of your holes are. )
Live rocks, sand, grass...up to how many you want
from home depot for $5, and a light bulb for $10? remember around 6500K, don't go to high or too low.
I finished my Refugium for around $50~70

Oh, and a hang on used good condition skimmer only cost me $20

Hope this would help