I have just tested this pump, and at 120 RPM got a flow rate of 4 USGPM or 15 litres!

I hope no one minds me re-posting this here as I put it in the wrong place initially ("peristaltic pumps" in the equipment section.) And I do not know how to rename the title or move it, so perhaps a moderator could do that for me and put the previous posts here instead.
I will follow this up with more details if there is interest in others constructing these pumps, but for now it is looking very promising, and cheap.