WANTED: Pump

Has anyone got a pump they no longer use that I could either have or buy for cheap. We moved to a house last year with a pond, it was green and somehow the koi were still alive (they had not been fed for years and the old previous owner said there were no fish) We got it sorted, cleaned out and purchased 2nd hand equipment that was working very well. Unfortunately the pump has packed in and so we’re just running air stones. It’s turned green very quickly especially with the weather we’ve recently had. Pond is roughly 13,000 litres. So something that can withstand that size. Based Midlands, but can travel if needed. Can’t afford a new pump at the moment and we’re trying our best to get the fish nice and healthy again. TIA