I use general purpose livestock mag buckets with garlic Very sturdy, no molasses and last ages.
Specifically horse ones though I would recommend Equiform Nutrition Paddock Bucket - again no molasses so no ripping and digging apart.
Best one is local one made for your areas deficiencies in minerals etc. So I use Norvite pasture block with garlic as am in NE Scotland. It is molassed so licked rather than chunks bitten off....
I use one from Dengie called "Lite-Lick Garlic". About £13 for a bigger pot than Horslyx, and he loves it. getting lots of vits and mins down him, plus the garlic helps repel the flies. One lick lasts about four/five weeks. I think I'm lucky in that my boy only takes what he needs.
I tried the Dengie Paddock Lick (big round one), they ate it in 3days! Meant to last 3 weeks. Now they have himalayan salt lick in the field and NAF pink powder in their feed for vitamins and minerals.