The fuel pump in my car died, its standard inside tank 2003 Hayabusa unit.

Engine is mildly tuned with a bit of head work and cams installed, everything else is standard.

Do I go with another second hand pump or is there a viable alternative to a very expensive OEM pump?

You do not necessarily need a Hayabusa pump as most Suzuki fuel injection pumps will do and Busa pumps tend to hold a premium on eBay. You can also replace just the pump from inside yours for very cheap money. https://www.ebay.co.uk/itm/OSIAS-EFI-Fuel-Pump-For-1999-2012-Suzuki-Hayabusa-GSXR1300-GSXR-1300-1300R/263560089888?epid=5016832305&hash=item3d5d67 d120:g:kHYAAOSwLopasLMh

Cosmick

I went with this pattern replacement, seems good so far

Fuel Pump

OK glad you are sorted.