The easiest avenue as you know would be to find a new remote. I don’t know if any of the dealers in your area would have one in inventory, but I would call or email a dozen or so and ask if you have not done this. Might be a long shot. The UltraLegs web site has a dealer listing that might help.
My understanding is that the standard remote is not Bluetooth. However, if you want to use your phone as a remote, you will need the Bluetooth “box” that plugs into the area by your pump and switches. (I assume your manual switches are working). Then you would download the free Ultra Legs app from your App Store.
I purchased the Bluetooth equipment on my last pontoon as I wanted to use my phone as a backup but I really didn’t use it. It was easy to install. I left it on my pontoon when I traded it in. The new owner probably doesn’t even know he has it.
The attached instructions may give you more background info.