Even though you already have a 45mm prime, maybe you should consider the m43 macro lenses like the PanaLeica 45mm f2.8 and the Olympus 60mm f2.8 if you really need such short focus distance. It doesnt sound as if other normal lenses that have shorter than usual focus distances would satisfy your needs.
All lens had a minimal focus distant, so if you have reach the MFD, then there is no way you can go nearer unless you attached a closeup lens like the Raynox 250.
Don't just go about getting a macro lens though, first you need to know which focal length (wideness) of your lens that you are comfortable with. I would recommend that you get a Oly 12-50mm f3.5 - 6.3 lens. It can focus pretty near and had a close-up (macro) option. Not really a true 1:1 macro lens though. I have one and loved it, although not the same quality as the 12-40mm PRO lens, but it is good enough for most uses.
in my opinion, 25mm 1.8 is a good lens for food. Currently am using the 17mm depending on how close you want. If it is not close enough, can make use of the 2X feature in your em5. 25mm is equivalent to 50mm full frame. Light for travelling as well. 17mm may take the whole plate if nearer. My suggestion is to visit the Olympus showroom which you can try the lens, 25mm, 60mm, 12-50 or even 12-40 2.8 with the figurines on display at the centre. You will then have an idea what to get.
I'm waiting for the 25mm price to come down too but the GSS prices so far not so attractive.
I use the Panasonic 20mm f1.7 for food pictures. The focal length is just right and it works very well even in dimly lit restaurants. I find that with a 25mm lens, I struggle a bit with some angles if I want to catch some dishes in their entirety. 45mm is way too tight and its MFD is 0.5m. The MFD for the Olympus 25mm is 0.25m. For the Panasonic 20mm, the MFD is 0.2m and as a pancake lens, it doesn't draw as much attention