The companies other posters have listed are all great to do business with. Some companies I use to get supplies such as cleaners, lubricants, etc. are:
Ames Supply
www.amessupply.com
Image Supply Service
www.imagesupplyservice.com
Good luck with your venture. Always remember to protect yourself----don't do business with just a handshake.
Put everything in writing. I don't think you will have too much to worry about as far a conflict of interest is concerned with you're primary employer, unless you signed some sort iron clad "no comptete" agreement when you were hired.
Again best of luck.