CR2 or Below creatures that can help me succeed a wisdom check?

Okay so I NEED my co-conspirator to pass a DC18 Wisdom check for a competitive D&D oneshot. 2014 RAW only (so things like changing spells for creatures in MM might be disallowed) for myself. Thanks to Portent/Embolden Bond/2024 Heroic Inspiration, he has 4 d20 rolls + 1d4 to hit the DC18. Thanks to some BS that's technically RAW, I can get a CR2 or lower creature to assist me. So far I've found Duergar Keeper (Enhance Ability) but are there any other creatures that would help?

I'm specifically wanting like either Bardic Inspiration or something like flash of genius. If it's really good and can deal fire damage, we can do CR5 or below since the boss will be under the effects of 2024 Hallow (vulnerability to fire)

It's for a competition so BS readings or OP stuff is totally fine (eg. Ring of 3 wishes as Genie Warlock vessel).