Even better - check this out: https://techship.com/products/telit-lm9 ... gps-mpcie/
I don't know if this forum allows external links, so in case the the link is deleted - Telit LM960.
Even better, you can check ALL Cat.6 LTE cards https://techship.com/products/category/lte-cat-6/
under the same roof, and pick one or two of your liking.
This site, techship.com is a good Swedish one. You will do the community a huge favor if you can get your hands on one of these mPCIe cards and test them in a MikroTik.
EDIT 2: I totally forgot about https://wiki.mikrotik.com/wiki/Manual:Peripherals
. There you can check for a list of somewhat supported mPCIe LTE cards, and then pick one that possibly does the job.