Which outdoor filaments for unheated beds?
PETG is good for your project.
You can also print transparent ABS on unheated bed with ABS juice.I tried transparent ABS in outside environment and it work fine.I live in India where outdoor temperature reach to 45C in summer.It is easy to print small parts.ABS juice may or may not work with large parts depending on your ambient room temperature.Ambient room temp should be above 30C for ABS on unheated bed.I suggest you to use a enclosure for printer if you are in cold area.