A28 Pilot encounterd unexpected icing conditions during climbout and elected to divert to ZZZ. Reporter had difficulty locating ZZZ in his chart reader.

Narrative

My wife and I departed for our destination after a lunch stop. Arrival from the west had been uneventful with a descent through clouds and ceilings about 3500-4000 MSL. Tops of that layer had been at 5000 MSL with several thousand feet of clear air before another thin layer from about 9000-10000 MSL. On departure; we entered clouds at 3000 MSL; a little lower than expected. We flew out of that layer at 5000 MSL having picked up about 1/8' of clear ice on the temperature probe. (On our Piper Arrow; the temperature probe is easy to see and accumulates visible ice sooner than any other part of the airplane; making it an ideal 'early warning system.') I was surprised to find another cloud layer almost on top of the first and was back in IMC by 6000 MSL. The plane continued to slowly accumulate ice but I (foolishly) hoped that the second layer would be very thin and I would quickly climbout the top of it. At 8000 MSL we were still IMC and still accumulating ice. I received clearance for descent and lowered the landing gear and pulled the power back to get a 2000 FPM descent to what I assumed would be clear; warm air at 3000 MSL. I was dismayed to still be in IMC at 3000 MSL with ATC telling me that we could not descend further at our position; just west of the ZZZ VOR. ATC offered the GPS 16 approach to ZZZ as the closest option and I took it. We flew in IMC until descending below 2900 MSL on the final approach. By that time; we had over 1/2' of clear ice on the temperature probe. Air temperature on the ground was just +1 C. I use an e-book reader with a subscription to NACO charts to give me approach plates for the entire country. My wife and I had significant trouble locating the approach plates for ZZZ. Our GPS; a KLN94; provided lateral navigation but no descent profile so this was a significant problem. Fortunately; another pilot radioed the MDA to me and my wife eventually able to pull up the approach plate. I made several mistakes on this 18 minute flight. Among them: taking off without rechecking METARs and PIREPs; assuming that the weather east of our lunch stop would be essentially the same as the weather to the west; continuing the climb into the second cloud layer; and not immediately returning when I climbed out of 5000 and saw clouds where I did not expect them.