Sidesteps are available new from several suppliers in your neck of the woods, brand new; look in 4x4 magazines for suppliers, and compare prices.

Secondhand items can be found on this site in the classifieds, and in many other 4x4 sites classifieds.

Waxoyl kits can be purchased to do it yourself, but put plenty of paper or dishes down to catch it when it runs out of chassis members. Several local garages will do it for you at a price, it is a case of ringing around.
Many people i know club together to do several vehicles at once, the cost of the kit is then equaly shared among you all, and you can do future vehicles.