Cheapest priced copy (Teenage Mutant Ninja Turtles Eternal): $39.99 at Card Kingdom, foil, near mint, their price list as of .
Commander's Plate 
Artifact — Equipment · Mythic · Commander Legends · #305
Equipped creature gets +3/+3 and has protection from each color that's not in your commander's color identity.
Equip commander {3}
Equip {5}
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
7 printings · $39.99 to $119.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends | 305 | Mythic | $47.99 | $64.99 |
| Commander Legends | 692 | Mythic | $69.99 | $64.99 |
| Commander Legends Promos | 305p | Mythic | $69.99 | $119.99 |
| The List | CMR-305 | Mythic | $49.99 | — |
| Secret Lair Drop | 1339 | Mythic | — | $74.99 |
| Secret Lair Drop | 1733 | Mythic | $47.99 | $39.99 |
| Teenage Mutant Ninja Turtles Eternal | 135 | Mythic | — | $39.99 |
3 rulings from Wizards of the Coast
- 10 November 2020If your commander is a card that has no colors in its color identity, Commander's Plate gives it protection from each color.
- 10 November 2020If you have no commander, Commander's Plate grants no protection abilities. The equipped creature still gets +3/+3.
- 10 November 2020If you have two commanders and attach Commander's Plate to one, it has protection from each color not in your two commanders' combined color identity.