If you supply a ladder I wasn't thinking of charging you to cut and weld it, although a pint of Guiness on one of our cruises goes down well.
It's an hours work which I'd gladly do one weekend whilst you wait. The ladders come up on ebay quite often if you keep an eye out.
The bottom mounts only have a reasonable size screw in the middle, they don't go all the way through.
If you can imagine a top hat shaped section with a hole through the centre, that is screwed to the transom with a blob of sealant behind it then the tube is slipped over the top and a small stainless steel bolt put through sideways to clamp it to the top hat shaped piece.
It needs to be firmly fixed as there is a lot of leaverage on it as you haul yourself on board.