I could be wrong, but it appears that the pump and reservoir are only sold as an assembly by Lotus. I would suggest removing the assembly from the car and seeing if you can remove the pump from the reservoir. If you can remove it, take the two into your local AutoZone or other parts store and see if they have a pump that will fit the reservoir. I would start by looking at a pump for a Toyota Celica (here is a photo of the one sold by AutoZone AutoZone.com | Vehicle Selection | Year
) and if that one doesn't work, look at their generic pumps to see if one will fit. I took a look at the reservoir on my Elise and it sure looks like a Japanese part. If you do find one that works, please post the part number and what car it fits.