Pallet Collar's

Can anyone recommend somewhere to buy used pallet collars.
I'm in the VERY early stages of setting up my allotment and want to start off with a few raised beds while I clear the rest of the site.
From what I see on YouTube its like pallet collars are falling from the sky and everyone's using them but I'm struggling to find anywhere that will sell them apart from in bulk.

Any advice would be greatly appreciated.

DD

Facebook market place has been handy around here for them £6 delivered

They seem to be out of stock of single units at the moment but worth keeping an eye on them.