Your lips need protecting from the sun as well as your skin. For the colder months I like Apicare Protect Me Beeswax Lip Balm SF 15, $7.20 for 4.5g. It moisturises really well.
Alba Botanica Sun Lipcare SPF 18 Lip Balm is also good. It's $8 for 4.2g. So is Evolu Healing Lip Treatment SPF 15, $19 for 10ml.
For a higher SPF, I like Comvita Lip Balm SPF 30, $11 for 5g. Or try Dr Hauschka Sunscreen Stick SPF 30, $26 for 4.9g.