For pods I would recommend Hitchcocks - yes, the Royal Enfield dealers - who supply S&B filters which IMO are every bit as good as K&Ns. Have a look at their site. I bought four for my 750F2 at around £60 inc. VAT and P&P.
For mains, I've always used Allens Performance. Very helpful and very quick delivery. Never bought slows, so don't know if they supply them.
As has been said, don't chuck away the original parts. You CAN get pods to work, but it can take quite a bit of trial and error to get them right. Good luck!