Your options depend on your GM more than the rules as written when it comes to this, given that no such items exist. Even with custom magic item crafting, a mechanic built into the game, the GM has the final say on whether an item is broken or not. Here's the options that you would have to work out with your GM if you want those two items.
Option 1: Re-Slotted Item
If your GM is fully supportive of custom magic item crafting taken to its extreme within RAW and your character doesn't need one of their other slots (perhaps ring, chest, or head, depending on your build) and you have access to a magic item crafter (I'm assuming you can't craft this on your own), then you could simply hire the crafter to craft an item with the same properties as one of those two items in a different slot. As a GM, I could see the Wrists slot being a reasonable substitute for the Amulet of Mighty Fists, given that it would clash with the Bracers of Armor, just as the classic conflict for a Monk's Neck slot would be Amulet of Mighty Fists vs. Amulet of Natural Armor.
Option 2: Combined Effects
If your GM is familiar with some of the shenanigans that can be pulled via Craft Wondrous Item, he might disallow changing the slot, as is recommended by the rules for magical item crafting. You could have the abilities of one item crafted into the other, which is allowable under RAW and provided for under magical item crafting. As a GM, I'd be okay with this, due to the extremely high gold costs involved, which limits your resources that can be used for other magic items.
Option 3: Un-Slotted Item
Similar to Ioun Stones, you might be able to make a "charm" of some kind that lets you have both effects. An easy option would be a magical tattoo that grants you the full benefit of one item or the other. More expensive than even combined effects, but still possible.
Option 4: Pseudo Hand of Glory
It's possible that your GM would rather let you craft a custom magic item that allows you to substitute one slot for a neck slot, similar to to the Hand of Glory. You could theoretically have one crafted, but this is the likely option for GMs who don't like magic item crafting but are willing to work with their players to make sure they get the items they need. As a GM, trading one slot for another is an established precedent in the game, with the most common slots traded around being ring, body, and neck, so this also seems reasonable, assuming the other slot is a ring or the body.
Option 5: Pick One
Sometimes, GMs don't allow custom magic items, either by your hand or theirs. If this is the case, hopefully they're fair about it and aren't lowering the hammer on your dreams but letting someone else have their unique doodad.