I haven't really played Mercenaries much, so most of this is theory crafting, but:
Ramshackle Power Armor gives +10 Accuracy, but -10 Evasion. It also has 20% Kinetic Resistance (35% total from Tough 2) and 20 Defense.
Pump King's Platemail has the highest Fortification right now at +50, but slightly lower defense than the Power Armor, and no extra Kinetic Resistance. No Evasion penalty.
I've found the
Custom Shock Gear to be really good on my Melee Tech Specialist. Stun Chance, Bonus Hit Rate, a small amount of Fortification and 6% extra Crit chance is a great combination. While it doesn't qualify for Low Tech Solutions, the +20% only applies to base weapon damage.
You might consider the
FZR Fire Suppression System in your Ranged slot. It inflicts Deep Freeze, which lasts 4 rounds, reduces Evasion by 50 and causes Crushing damage to automatically be Critical Hits. FZR doesn't benefit from Second Shot, so it's not really a good weapon for Ranged primaries. The Evasion penalty may make the Saurmorian Hammer more viable as well.
Picking up the
Salamander Defense System might be worth it, since you more or less expect your Shield to go down.
Santa Hat gives +50 Fortification, if you just want a massive HP total.
Signet of Bravery gives +25 Fortification, but also increases Physique by 5 (only 2.5 more damage).
Note: While the Codex currently doesn't show your Evasion below 1%, you do take extra damage when you have negative Evasion, so -20% (-10 Power Armor, -5 Saurmorian Hammer, -5 FZR) might not be worth it, I don't know.
