The Shimano XT hydraulic disc brakes on the Salsa El Mariachi Ti seem to need bleeding†, but one of the tools that I had to purchase before doing so was some vinyl tubing for the caliper end. I found that Watts Polyurethane Micro Fuel Line, 1/4″ OD x 1/8″ ID seems to fit perfectly. As pictured above the ID slips snugly over the bleed port on a Shimano brake caliper and both the ID and OD fit nicely on Luer lock syringe. At ~$5 for a 10′ roll at Home Depot one has to purchase much more than is needed for a single brake job, but it could easily be shared with friends.
† First symptoms were the brakes rubbing slightly after a sustained descent. Now they are rubbing for a brief moment after almost any use. I suspect there is air in the calipers and it’s heating and expanding, moving the pistons outward. Bleeding should address this.