Honestly, if you strike out finding a shop, look up the backing plate size and weight rating of the existing surge brakes and get an electric brake kit for it. Since its not a boat trailer, submergence is not an issue and you'll be able to live dial the braking impact the electrics trigger while testing it with a live load.
Electric conversion kits used to be fairly inexpensive since it was mostly just a swap of the hydraulic cylinder for the electromagnet piece designed to take its place and running of some new wire to your trailer plug if you are already wired up for electric trailer brakes on your vehicle.