which type of visa do I need? I have no business registration papers yet.

Well, seriously you should apply for a M type. It means that you need to find a Chinese trade partner to send you the invitation letter. But I think you may just use your L type to buy equipment. In order to apply for a L type, you should provide your passport, filled 2013 version application form, a recent passport photo, round-trip air tickets, hotel booking and your financial proof, recent six months bank statement, for example.