companys wont entertain you, they get 10 requests a day, to get in with them its usually done by a promoter who has the right connections, so you need to be fighting on fairly big stages to meet the right people for that
Go into local supp shops, ask for manager, if its something they do then they will contact their boss, arrange a meeting and bring laptop with few fights on SD card aswell as any promo posters you have from fights and explain/show them how you can advertise their shop, logo on poster, shorts, dvd's, facebook, sell product in gym, hook them up with free tickets for fights which they can then use to bring out corporate partners etc etc
but chances are very slim mate these days, fighters are ten a penny
EDIT
your selling yourself here, dont walk in asking for sponsership, use a bit of savvy, walk in saying you have proposition to promote their business, you need a bit of patter or else it be a waste of time