I see Jolly Ann Marine (and IDO Sponser) has them listed or you could get at Cabelas, Thorne Bros, Capras, and most any other place that sells Lowrance.
12′ is part # 99-93
20′ is part # 99-94
http://www.jollyannsales.com/FFwithGPS/lowrance_accessories.htm
Here’s all the different models these cables will work on. The Elite 5 is listed as just a 5. Still the same.
Lowrance 12′ Extension Cable
Transducer Extension Cable
Availability:
Product # 99-93
•Transducer Extension Cable
•12′ Cable Length
For Lowrance Models:
•HDS: 10, 5, 5x, 7, 8
•LCX: 110C, 111C HD, 112C, 113C HD, 17M, 20C, 25C, 26C HD, 27C, 28C HD, 37C, 38C HD
•LMS: 332C, 334C iGPS, 335C DF, 337C DF, 339C DF iGPS, 480, 520C, 522C iGPS, 525C DF, 527C DF iGPS
•X102C, X105C DF, X107C DF, X125, X126DF, X135, X136DF, X510C, X-510C, X515C DF, X-515C DF, X52, X59DF