Unless you shave the post (0.2mm takes longer than you think unless you have a lathe), which probably won't be very uniform, it's never going to fit. If you get it in without modification, you'll probably seize the post in the frame. Last time I needed a post in an odd size I asked my local shop to order the cheapest aluminum post they could find (likely Kalloy or such). It cost me ~$12, and while it's a bit heavy, it turns out it isn't slowing me down any.