Look at marine suppliers for distribution boxes - Look at the dimensions obviously. I use this
I use one like this
It's BIG. and near fills the air filter box. But was cheaper. Everything I fit gets it's own separate fuse - nothing taps into stock wiring because it simply is too fine to trust in. Wires are terminated with crimped ring connectors for the screws and heat shrink.
Yes - OTT. But no risk of overheating, shorts, etc....
I'd STRONGLY recommend you always fit relays using proper relay sockets too. Why? - wait until you have to change one - at night in the rain on an unlit road.
I'd want to know if the FZ1 relay can be swapped out if it fails - The EB can. ime - use industry standard components - they're cheap and easy to find.