Where can I find someone to oversee my husband's (has dementia) and my affairs in case something happens to me?

If you can move, I would look into either getting on the list to:
- going into Air Force Village (Blue Skies) in TX - which is a wonderful totally comprehensive program from IL to AL to NH and hospice and all sorts of community based events within the 2 villages. It is pretty amazing, also you have great medical from UTHSC plus WIlford Hall & Brooke for speciality stuff
OR get on the list for the Armed Forces retirement homes. I have no idea where they all are, but there is one close to us (New Orleans) in Gulfport and it too is amazing. with "small houses" and there also is AL, NH & hospice. All newly built last 5 years too.

About the who to look out for, estate attorney's can give you suggestions of geriatric case managers who do this. Financial advisors also sometimes do this for long term clients and become executor of the estate. I think the hard choice is do you include extended family to be a part of all this; or leave your estate to a charity or school or whatever rather than family. Your situation is likely going to be what more & more will face as kids live far away, have their own life.

Perhaps do some reading as to how those that live abroad deal with this, as they often have someone back in the US to deal with finances and end of life situations
that isn't family but paid to be an advisor. Good luck.

I am an only child with no children, thus have no one to pass on the baton... thus when I went to an Elder Law Attorney, my Will/Trust was written that if my sig other is unavailable to take over my affairs, then my Attorney [actually the firm] will use monies from the Trust to pay for professionals to pick up where my sig other would leave off.

I would recommend that you and your husband [if he's able] talk to an Elder Law attorney.... see if the Veterans Administration offers such services.