How valuable is each magic item slot?

For context: I recently made a mid-level gunslinger character who wields a 15 lb. double-barreled shotgun. This is a problem, because this gunslinger only has 7 STR, so their light load is only 23 lbs. I wanted to solve this with an item that gave me continuous Ant Haul, and noticed that there already exists a wondrous item that does exactly this, but it’s a belt slot item, which obviously would interfere with a Belt of Incredible Dexterity.

In theory I could get an item with Ant Haul for a different magic item slot, but putting an existing wondrous item effect on a different item slot has to be very heavily regulated, due to the popularity of each slot, so my question is this: Which item slots would you consider of equal demand to the Belt slot? Or to bring it to a broader scope;

How high in demand would you consider each magic item slot in relation to one another?

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