The good news is that they appear to be standard and not custom. This means you should be able to get these from some concrete supplier. The biggest issue you have is that these suckers are heavy and most folks won't have a vehicle big enough to transfer them to your home. Check the yellow pages for concrete blocks or concrete suppliers if you have a vehicle that you can load a lot into. If not you should check the concrete contractors, and don't forget to get several comparable quotes.