Baking tins, I'm so sorry.
I just had my 4th straight MC too.
There's no getting around how shit it is.
I too have been told that they can't find an underlying cause, seems to be random.
I note what you say about wanting the ERPC so that you can have the genetic testing.
My last one I m/c at home- before I could get an ERPC- (frankness alert-don't read on if don't want to) and I was so upset it started because I really needed to know what that testing would show, so I went to the loo through a sieve and stored all of the bits in a tupperware in the freezer. When I had finished except for spotting and had obviously passed the sac I took the bits in with me and asked for them to be tested.
This went down like a lead balloon at the hospital as you can imagine.
But I was very clearly not going to move until they'd sent it off.
In the end I had to say to the consultant-'look I've pissed through a sieve for 5 days and had to look at all those bits of material, all you have to do is sign a form' but this did get the required result.
So if you can bear to put yourself through it, push hard for testing of this one as it will really help you decide where to go from here in terms of future testing and planning.
I'm so sorry you are going through this.