Re: the skull mask, I was actually in a similar situation to you! Given that I’m probably going to be signing on with the League for my first Empire experience in E5, I’ve been putting together some speculative kit, including a metallic mask. I know you said you’d rather source it than make it - it’s just I’ve had great fun making mine, and (after a bit of work) found a way of making masks that works pretty well. I hope it’s helpful!
The first thing I set about making was a cast of my face/head - it’s useful as a guide to get the proportions right, and helps give something to work around. Modroc/plaster bandage facemask (a bit icky to do, but not too bad if you take care/follow this or a similar set of instructions). Then, once that’s dry, dump a whole lot of cement into it, and let it harden - once it’s done, you can peel the plaster bandages off, leaving you with a concrete impression of your face:
I recommend trying to source some particularly hard concrete/cement for this - I went with the usual quick drying stuff, which is fine for most purposes but can start to crumble if you begin going at it with a hammer. As you can see, the brow line is beginning to disintegrate, and the nose had to be rebuilt (rather more pointily) entirely!
Once you’ve got this, there area few options for making the mask. Covering the model in tin foil and building the mask up in epoxy works pretty well for ceremonial masks (e.g. this, but it’s not very sturdy, and wouldn’t work as armour. I’ve been going with 1mm copper for my half-mask, which is just about soft enough to hammer it cold (I reckon very thin brass sheeting would work to give you a decent gold look), although, as you can see, it’s not very smooth :(:
As good as I could get it without a blowtorch to anneal it! By going through an entire pack of wet and dry it’s possible to get the worst dings out of it though - when I get round to decorating it later, I should be able to distract from them.
For your skull mask project, if you were going to make it yourself, I imagine the same approach would probably work pretty well - cutting out the nose piece from your mask, adding vestigial jawbones + teeth, and you’d look pretty terrifying, and suitably doctor-y!