+10 Etran's (Deviling) - 50% Neutral resist
+9 Imuke Upper Shield (Alice or Khalitzburg Knight with WK combo) - 35% Ranged resist, 40% Boss Dmg resist or 30% Medium/Large resist
+8 Siegfried's Helm - 20% Boss Dmg resist
Mob Set - 2-6% Demi-Human resist
Ring of Jupiter - 3% Human resist with 125 vit as well as a lot of def/mdef
Angry Snowier & Ice Titan combo - 20% Medium resist
Kafra Blossom - 10% Elemental resist (although I'd argue Errende Ebecee is generally more useful in Bio5 if you are using Angry Snowier combo and only have one accessory slot available)
There is also stuff like Palace Guard Cap and 3D Glasses that add neutral resist, but these aren't really worth considering for Bio 5.
What of these you should use is highly dependent on what class you plan on going in Bio 5 with.