Looks like the "el-cheap-o" gravel most Local Fish Stores sell around here! It is actually very coarse blasting grit! Basically it is just fine gravel. Most places here sell a 50lb. bag for $12-$14. So I would try looking at your LFS for it, or find a store who sells blasting media and go from there. IIRC the particle size is 2-4mm. I really like using it, but the last few bags I have gotten have been a little to light for my taste. I really like the look of the Carib Sea Kon Tiki!!! It looks like the older cheap stuff I used to could find cheap! I asked Big Al's about the grain size and they said 4-6mm, but I have seen a sample of it at our LFS and from what I remember it is smaller! SO I guess I will have to order a bag and see! The cheap-o stuff they have now looks almost identical ti the Carib Sea
Anyway I hope this helps ya out!