Mice were not typical in c64 era, so you probably won't need one, but the psu's and disk drives and all, when combined, are heavy. I strongly recommend a disk replacement of some kind and there are quite a few.

Those always make me think of the film "23".

Oh yes, sure. I think I have seen people using little screens that were designed to clip onto Playstations.

edit: you could also look for the SX64, a portable c64 with a small monitor and disk drive built in!

A little monitor will be better than a TV for live performances, assume that is possible have live sets with a commodore, but I'm not sure of this...

MSSIAH seems to be what you want - you can control it or sync it with MIDI to other gear.

I don't think you need a disc drive if you want to use MSSIAH, it comes on a cartridge. But I'm not sure, I've never used it before. You can just use a television as the monitor. It might be easier to get an old c64 mouse, I don't know if there are adapters to use lazer mice or whatever?

Online auction sites and forums are your main choices for places to buy stuff, try to get your head around ebay because there is a lot of stuff there.

I'd really like to try this adventure, but I'm not sure if I know how. Obviously I need the console, 'cause I prefer don't use emulators, Then I need a tiny monitor, the AC adapter, a floppy disc reader, and an adapter for use a mouse of today. Is it right?
After I have to choose a program, at the moment it seems to me that MSSIAH will be the simplest choice, but in this case the C64 will run like a workstation, alone. Maybe I think wrong, but in my project I'd like to have the C64 like another instrument in my set up made of gameboys and synths playing together. There's a way to sync them?
After all of that, the big question: Where's (possibly in Europe) the good place where buy all the hardware? 'Cause e-bay confusin' me.
Not sure if I explain myself well and sorry for my poor english.
Thanks!