I know about the SXT LTE but I need a fully outdoor solution with LTE and UMTS/HSPDA.

Who has found a multiband antenna with space for the mikrotik radio?

Haven't seen multiband antenna with a pouch yet.
Go for the poynting XPOL, and the RB in a weathertight box.
Sierra MC7710 (discontinued) can be found on Ebay at an affordable price, and covers most of the bands. I use it in the RB912.

Fibocomm L810 is a great and affordable mPCIE LTE card.
it supports many bands and is backward compatible with 3G and edge.
you can buy it from TME. or from this guys: http://www.macrobudapest.hu/about-us/

the folks in budapest have good connection to the manufacturer and have the latest firmware available,
whereas TME just sells the board w/o support. and to be honest, the vendor itself does not provide any
downloadable material, just the brochures.

i have couple of them working with RB912 (Basebox). the only stuff you need to be aware is that the modem
will not be detected at the boot (probably the power is applied too soon to it) so i always need to run a script by
ROS scheduler to see whether the port is inactive and do an usb power-reset.

and despite the L810 is an actual LTE device, ROS currently does not see it as a direct-ip modem, but only as a PPP
device, so it will not be shown under /interface lte.

device's brochures found on the following link: http://www.fibocom.com/upfile/down/file_2_3_3_1_2_1.pdf