That's how I do it. Its sketchy!!Easier with two people a hulk to push it together and one to start the bolt . I used a 2x4 to wedge it in place with one have and other to start the bolt. Just make sure you got at least 3 threads started or it may blow back off at ya.
Oem is a banjo fitting 10mm 1.25 pitch. Oem is around $40 I think. I think this one would probably work for $10: Universal Hydraulic Brake Light Switch Banjo Bolt 10mm x 1.25 Pitch Motorcycle | eBay