A regular SPF lip balm is fine.

Use what you have. Any lip balm with SPF 30 or higher will protect your lips from sunburn, and that’s really all that matters.

The whole “separate lip sunscreen” thing is mostly marketing. Your lips are skin, and SPF works the same way there. The main difference is that regular sunscreen tastes terrible and isn’t designed to stay on wet lips. So yeah, use a lip balm with SPF.

But you don’t need a fancy “lip sunscreen” product. A ChapStick with SPF 30, a tube of Sun Bum, or even a tinted lip balm with SPF will do the job. Just reapply after eating or drinking.

Don’t overthink it. Sun protection is sun protection.