I am looking to add trim on the throttle to my boat. I would also like to have a button for the trim tabs.

Does anybody know where I can get something like this? Maybe Gaffrig (either one)?

I have Morse throttles.

I have a trim switch by Rex Marine on my morse throttle. While it's not as natural as the in throttle controls, it's perfectly acceptable. The hardest thing is trying to route the cable through the shifter so it doesn't catch, pinch or work harden.

Here is what I have on mine
it is a single switch that is controlling both drives
This winter one upgrade I am doing is to install the twin button one for each drive.
I usually have to touch up on drive or another on the cat to level out. I have the main drive switch right under the throttles but I have to remove hand to get to it.
Would have quicker and saver reaction time to have individual drive switch at my finger tips

http://www.rexmar.com/page40.html

I have the second one pictured for left hand to operate my center tab
I do remember seeing one somewhere that branches out to both left nad right for tab control on the steering wheel. Might be Eddie marines

http://www.rexmar.com/page41.html

MnFastBoat - so if I buy the dual switch one, I can have one operate both drives and the other operate both tabs?

yup you can do that just use diods so that you can trim them independently if you need to.

Jon