You could always make them yourself from wood, it can look really good
These are almost 10f long, they were pretty costly to make. However, that's mainly because of my choice in lighting/heating/type of wood/thermostats/laquer. Purely the base of this construction (Glass/Wood/Sealant) was an estimated 750 / 800
€ If you keep the constriction simpler (skip the openings in between, and decoration), and use a cheaper wood. I am sure you could build them for less, especially since you're looking for smaller sized enclosures.