Equip Armor on Tameable Mob

So I've got a tameable biped mob, I'm relatively new to MC modding so I figured I was doing something wrong. But as I searched I found this:
Can't change held item/armor on Tameable Entities (ingame)

I'm hoping there's a solution, but as it stands the only thing I've been able to learn so far through testing is that randomly when right-clicking over and over again with an item I'm sometimes able to get them to equip it. I didn't think it would be this hard or challenging to implement considering horse armor is a thing, yet still- no dice.

Any advice or a workaround? Does anyone know if a GUI inventory would work somehow, and if so- could you please send me an example? I just need the player to be able to equip a melee weapon, armor and or shield onto the mob they've tamed- and for it to actually show up. (I am not using custom models right now, this is almost entirely vanilla with procedures).