For the shield it depends on what flavor of damage you're interested in doing and how much you want to lean into the proc-on-crit-prevention mechanic shields. The shield that directly contributes the most damage is probably Shield Orb, but that of course necessitates that "damage" means spellcasting (with or without your spear). In terms of pure defensive stat contribution, by far the numerically strongest shield available is the Thornshield, but it requires you to proc it frequently enough to maintain the buff.
For the spear it's more straightforward, depending on how inclusive your understanding of "spear" is (you don't have to look far to find people willing to fight over whether glaives, pikes, tridents and so on count). If you're committed to spellcasting you probably want the Storm Glaive, If you're Charming you take the Jassiran Glaive instead, and if you're doing neither and/or you don't think glaives count you take Caranbrot. Caranbrot also happens to be the best spear for improving your shield proc rate, which most of the other spear and spear adjacent options work against by giving you evasion.