Here are all the items that grant the highest block % in each slot:

• Helm: Helm of command 8%
• Ring: Justice Lantern 11%
• Belt: Kotuur's Brace 5%
• Weapon: Doombringer 7%
• Pants: Captain Crimson's Bowspirit 4%
• Shield: Stormshield up to 34%

With these items, it becomes nearly trivial to get the achievement. However, note that some of these items aren't max level items so they aren't optimal for actual use outside of getting the achievement.

Here are all the items that grant the highest block % in each slot:

• Helm: Helm of command 8%
• Ring1: Justice Lantern 11%
• Ring2: Legacy Justice Lantern 11%
• Belt: Kotuur's Brace 5%
• Weapon: Doombringer 7%
• Pants: Captain Crimson's Bowspirit 4%
• Shield: Stormshield up to 34%

With these items, it becomes nearly trivial to get the achievement. However, note that some of these items aren't max level items so they aren't optimal for actual use outside of getting the achievement.