You can get a barrier block from a shop if you first grab an item you can sell to a shop and then change that to an item you can't sell, you drag the item to a barrier slot and then you can swap it for a barrier, you can't but the barrier in your inventory though so you drag it next to you inventory and leave the shop, this drops the barrier on the ground and you can pick it up.
You can get a barrier block from a shop if you first grab an item you can sell to a shop and then change that to an item you can't sell, you drag the item to a barrier slot and then you can swap it for a barrier, you can't but the barrier in your inventory though so you drag it next to you inventory and leave the shop, this drops the barrier on the ground and you can pick it up.