I like the leather weaver skid boots. They have velcro so they are easy on and easy off. The sand does not stay in them too bad. They are not cheap but well worth the money. They hold up well too. The horses do not seem to mind them.
I like Pard's leather skid boots. They have a Velcro closure, soft leather sling type lining inside (it has some give to conform to horse), don't trap dirt, and good durability. Not the cheapest... but none of them are, and they are all "consumable", meaning you will eventually wear them out and have to replace. The time you get before they wear out just depends on the footing.