Spare wheel for 2015MB C250D Estate AMG line

[dfurdog]

Hi Newbie here, I have a 2015 W205 MB C250D AMG line estate and want a spare wheel for it, however Mercedes say they do not supply a spare wheel even as an accessory and insist that it is not needed as they supply foam and compressor and roadside assistance.
I am travelling through Europe this year and am not happy going minus a spare.
The issue is the 18" AMG wheels, the rear wheels are wider than the front ones with different offsets and I am looking for a "one size fits all" solution to my spare wheel problem, that will be safe and not damage the car in use
I would prefer a steel wheel as alloys are horrendously expensive and its only ever going to be used as a spare.
I can't find anyone at the dealerships who will advise me as they all insist a spare is not necessary. Any ideas where I can get sound advice and purchase a spare wheel.
Thanks

 

[kam05]

Must able to get a space saver wheel for a w205? If not then one from a w204 might fit?

 

[dfurdog]

Yep tried that, they only do a 17" and I am told it wont fit, not to mention the price of over £400, basically forget Mercedes for this one, they are not interested and insist its not needed as per my post, what I need is some advice re my post. thanks