I would try Film Plus in the west end - symington and dupont I recall. A most personable shop.
They likely either have some yto rent, or someone who works there will rent you one.
I presume you will also need film holders and maybe a changing bag.
You have sorted out development and what it will cost?
PM me if all else falls thorough. I can get you fixed up with a cameras for a week or so and process 4x5 in a sink line on hangers, if no one else will.