I use cloches when they're small.

There's also sleeves that you fill with water that wrap around the small plants so as to prevent them from freezing when the temp gets low.

If you need bigger there's plenty of fairly large 'pop-up' greenhouses you can just put over the soil.

Here is a link that might be useful: Popup greenhouse

I think you could make a hoop house for less money and it would let more light through.

Yeah, I just used that one as an example. Hoop houses would work great too. There's much cheaper plastic greenhouses too - I didn't realize the one I linked to was so expensive.