I built my own. I use the OEM blank slots, with custom push switches. This way if a light or relay goes bad, I can track it and easily replace it or the fuse. I can run 5 things requiring relays and 5 straight fused. So when I added my radios for comms, I simple ran the 2 lead wires and added the appropriate size fuse in the box.
There are multiple places to buy a fuse/relay box, and some sell prewired. That looks like a nice alternative. I use 3 spots for lights, 2 for comms. I still have 2 blanks.
***Disclaimer : my in a stock SR5 so no heated seats)***
Dades Bluegirl build