i bought my side steps for my p38 from a main dealer via ebay , they were sellimg off old stock , it was a complete kit with everything needed but at , a very reduced price .
along with the brackets you will also need the nutserts which go into the chassis rails and allow you to bolt the brackets to the chassis .
if the fitting kit is available i think you will be lucky .
whilst its not rocket science to fabricate the brackets it will be awkward , from memory i think that besides being handed they are also different front and rear.
maybe a breakers yard could help and the nutserts which are either 8 or 10 m/m are readilly available at most motor factors , and by using a bit of ingenuity you can install them into the chassis without the special tool ( i just used a long bolt with a nut and washer , it worked a treat ).
i hope this helps.
rick.