I did this
bought a Confer brand ladder
look up confer plastics, the have many " A" frame ladders.
Pick one and also order a deck conversion kit.Make sure the ladder you choose will accept the conversion kit, appears 4 or 5 of them do.Use it as a A frame ladder, when needing to mount to deck, you cut the back legs off and attach the deck kit.Basically sliding 2 pads with legs into each hollow opening left when cutting off, just double measure when cutting.They also have extension kits, which I needed since my deck was a little tall for the ladder.Very strong but the safety barrier is a little annoying since upper portion like to come loose.
I removed after the 2nd year.
couple links below
Products | Confer Plastics, Inc
Pool Ladders A-Frame