The cheap way to do it is to get a bunch of 70v hi/low audio transformers.
Take the low side of each transformer and plug that into the scanner. Take all the high ends and tie the leads in parallel, Take a additional transformer and tie low side to the speaker and the high side to your source high side. Radio shack sells the miniature xformers.
$10 and you have a multi way speaker combiner.Not as fancy as the fleet product but also cost hundreds less