Try these for profile they are cheap and quick delivery despite being in Germany. I buy my profile here and they are very good with accurate cutting.
http://www.motedis.co.uk/shop/Slot-p...91_999993.html

Tip with the gantry profile if you use Bosch rexroth BR type profile 90 x 45 then the BK/BF12 bearing holes match the slots. With Item 8 series type they don't and you'll need to make plates for mounting. I Make machines that use L shape arrangement with 90x45 and they are more than strong enough so don't worrie about using shorter widths.