Don't know what cement manufacturers are in your area but whoever it is go to their web site and see what's available. The manufacturere in my area is Quikrete and they have 94lb and 47lb bags of portland. They make a sand/topping mix that you can use that comes in 40, 60 and 80 pound bags. Trying to remember...think it has sand and cement premixed in the bag so you could just add your peat moss or vermiculite or perlite. Some people have been working with "Quikwall". Is there a garden club or master gardener group in your area. Maybe you could contact those groups and see if you could split a large bag of cement with someone. Good luck! Billie