Budget 6 speed shifter and derailleur

[Okeydokey]

I'm looking to add a derailleur and shifter where the last one had been removed on a Raleigh Vixen. Previously it was a twist grip but for the purposes of this exercise I would like to add a trigger mechanism.
If I go down the SRAM route, I can find the X3 range which provides for a 7 speed mechanism. Any other reasonably priced options spring to mind? And where can I find a reliable supplier...

Edit: Meant to ask, can I use a 7 speed derailleur and shifter on a 6 speed bike?

 

[Arjimlad]

Just a thought - 6 speed bikes are usually freewheels rather than cassettes.. would this be a good time to put a 7 speed freewheel on ? Might widen your choice of shifters..

 

[tyred]

I would use this shifter - http://www.ebay.co.uk/itm/6-SPEED-R...561?pt=LH_DefaultDomain_3&hash=item2a506adae1 for a 6 speed system and it should work with a 7 speed derailleur.

Have a look in the local dump/skips/river you may even find what you need for free.

If you want to go 7 speed options, then I think there is a 7 speed version of that shifter too if you look. Changing to cassette hub should be easy on a mountain bike but may cost more than you are willing to spend on it.