Yep,

You can buy he spring by itself. BAR, as above, or also direct from V-Mach. Just google up the site. You can ring Steve direct.
For that extra bit of refinement, unless you have a lathe and can turn up your own guides, push the budget a little further and ask Steve to do you a spring with matching guide and top hat. Whilst you're at it, go for the piston sleeve as well.