Hello;
     What do you want to connect to the Profibus? If it is a PC computer, try SST/Woodhead. I have used some of their products.

jazznska
Profibus connected to industrial ethernet is known as Profinet.
The following link explains more on Profinet: http://support.automation.siemens.com/WW/view/en/21456620
For more help I would suggest advising the type of equipment you have (type of S7) as your description is a little vague in the Simatic world of S7. Also, as djs hints, what are you trying to do?

Jazz,

 You can use a Siemens CP5511/CP5512 and Simatic Net PC card (plug and play) to connect via MPI or Profibus at any location on the bus. If the PLC is a soft PLC such as WinLC controller and is installed on a PC670 HMI for example, you can connect via a crossover cable and TCP/IP network connection. Regardless of the protocol you must first set up the interface via the Set PG/PC Interface from the Options tab in Step 7.

The S7-200 is different from the S7-300 and 400 series in terms of hardware and accessories. As sed2developer said, your need to start by determining which version you have.

JRaef.com
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Its been a while on siemens but I remember!

I know their was a simple special manufactured db9 connector that converts from the Siemens Profibus/programming driver to Ethernet.  Costs was pretty low, $300, but that was a few years back.  I am sure its still out their but better.