Besides those found in pathfinder 2e, what sort of healing items exist in SF2e? Im specifically asking about if a party doesnt have access to a magical healing. I know battle medicine probably exists, but what about the old healing serums from 1e? Did I overlook something?
Yes, Battle Medicine exists, and works just as in PF2.
For now, healing items from PF2 are NOT available in Starfinder, unless you are allowing them in a home game. (The GM Core book has a chapter of rules for mixing the streams, but I haven't read that far yet. And Society only allows SF content, very VERY few exceptions.) There are, however, spell ampoules, spell chips, and spell gems, which can contain spells for later use.
Medpatches are no longer just for first aid; they have taken the place of healing serums as the primary "leveled" tech for restoring HP.
Hypopens help clear conditions and affliction, either by reducing a condition's value, or making a counteract check against an affliction. The higher levels can provide some beneficial boosts instead.
Serums are pharmaceuticals with a variety of effects.
Sprayflesh allows you to Treat Wounds again before the usual immunity period ends.