What else do I need for my regulator?

You didnt mention a CO2 tank but I am assuming you know that already, otherwise it looks like you have everything. How are you going to diffuse the CO2 into the water would be the only possible thing you are missing.

The general setup is cylinder --> regulator --> solenoid --> needle valve --> bubble counter --> diffusor.

You have mentioned everything but the cylinder and the diffuser. You can get a parker solenoid on ebay for about $15 or a clippard one from various aquatic stores for around $35.

Do you mean teflon tape around the regulator gauges? Just a note about teflon tape; I recommend not using it as a small piece could come loose and then get stuck in the solenoid, preventing it from shutting off the flow of CO2. A better alternative is to use non-hardening pipe compound (pipe dope).

Also, for the regulator, I assume you know you have to remove the large hose barb, which will leave you with the (presumably) 1/4" port. You can then get a 1/4" to 1/8" nipple to allow you to connect your regulator to your solenoid.

The Parker solenoid that airbone r6 mentioned is good; it is the one I am using. Do note that you will need to find an electrical cord and attach it to the solenoid yourself. The easiest way I have found of doing this is with spade connectors.