Use the HPI Vintage wheels which are 26mm front and 31mm rear. Or any other wheels that have a built in offset to them.
The difference between a 190 and 200mm body is actually very small (ie. only 5 mm wider on each side at most).
Use hex wheel spacers between the wheel and the hex hub, also use a thin wheel nut like the HPI thin wheel nut.
Kawahara also makes M4 wheel nuts (standard wheel nut size) that doesnt use a nylock element but has serrated flanges (ie.it's thinner and it actually tightens up as it tries to loosen itself up, the serrations dig in to the wheel etc)
The Kawahara one's are aluminum/anodized or you can get steel one's from http://www.vxrracingusa.com/prodM_acce_NFS-0004.htm
The vxr one's are just like the regular nut and bolt place one's but they will do the job. These are awesome for nitro cars, as you're wheels will never accidentally come off, I use them on the front wheels of my electric TC when I'm running a spool.
Note: I actually work at hpiracing usa, graphic designer etc. I make decals, logos boxes etc. I also paint and prepare a lot of our show bodies. And whenever we are short of 200mm display chassis, we use the afforementioned parts (spacers, thin wheel nuts, offset wheels) to build up our display chassis/body.