I sold a 24" Sun trike to a co-worker. It had 24" Skyway mags made for trikes in the rear and a Skyway 24" front mag in the front. Person I purchased it from gave me the original spoke wheels as well. I can't recall who the retailer was but do a Google search for 24" Skyway trike mags. I'm at work and my phone goes sloooow because I'm in a dead zone.
Honestly their not that much heavier. I think Skyway list the weight so you can compare the weight to your spoke wheels. My Sun trike was already on the heavy side to begin with and I don't think the mags really changed the overall weight that much. I also didn't notice any handling changes, still rode the same.