I’m looking for a simple autopilot

In many cases the pump can be used with another brand of autopilot. Just find the autopilot you want to use and check with the manufacture if the pump will work with it.

What with all the advances in electronics these day I'm not sure there is a basic unit around anymore. So I suggest just the least expensive unit you can find from one of the reputable manufactures and go from there.

Perhaps look for a close out sale on a last years model kind of deal if you don't want buy used.

I also have the Garmin 740s chart plotter. This season I added the Garmin GHP 20 Autopilot. Like you suggest, I mainly just reach up and push the button and have it steer the boat. It works very well. I highly recommend this unit. Especially if cost is not the big factor as it is a bit pricey with install.

I have used a ComNav basic unit on a 49 Grand Banks and found it very user friendly, they have a good reputation, do a lot of commercial business. You should give them a call and discuss your objectives.

ComNav

Another simple unit is the Raymarine s1000, you may find a used one, not sure if it would work with your pump.

The 200DL is a pretty reliable unit, that's what we have on our boat. Have you discussed the situation with SimRad for repair or upgrade?

What size vessel? If money is not a issue then buy all new stuff; there is no value in trying to save an old pump which may have problems down the road.
The Simrad AP28(+ related system parts) I put on the 65 footer less than two years ago is simple enough. Turn it on and you go straight- you want to turn left? Turn the dial left. Turn right? Turn the dial right. While it's able to do all sorts of stuff I rarely use anything but the dial. It replaced a Robertson similar to what you have and the transition was easy.

Get a good installer to do the work if you can. I'm very happy with the AP28, and it's had zero issues so far.