What type of fuel pump should i use for a rover 1.4 K-series engine with multipoint injection?
Where would I go for one, and how much would it be?

You need to know the capacity of the rover pump in lph. A new one is over £100 from demon tweeks and alike.

VX injection out of tank pumps are good. Most pumps are the same size/shape and differ in that they have different size in and out connections. Good news with VX fitted pumps are they have 12mm push fit inlet and 8mm push fit outlet. This means that you can use normal injection fuel pipe and fuel clips. Cheap and plenty about. I've got a one off a 2ltr Cavalier and has been fine on 175bhp zetec.