Cost me $110 a few years ago at a hydraulic hose vendor. They made them up while I waited. If you go this route, make sure they have the correct equipment to do brake lines too. I ran into shops that said they could do it, then when I showed up with my oem lines in hand, found out they didn't really have the equipment locally, but would send it out.
Finding the junction at the bottom of the triple tree is the hard part. The Yamaha part is proprietary and not something you can buy. I found another part with a 10mm mounting hole that would work well. After that, it's about the angles of the fittings, unless you want to have standard lines with threaded fittings instead of swaged on fittings. I did this for the length and to eliminate the cross over line. I think I still have some new short Yamaha banjo bolts and copper washers that I ordered for kits, somewhere. The lines I had made were S/S braid with a plastic sheath over them to avoid abrasion issues. You can get them in several colors as well as clear. Some shops will also carry colored fittings as well. Hose color made no difference in price, fwiw. Fitting color did, (instead of plain).
And it's a lot easier to get exactly what you want if you walk in with your oem lines. Just pay attention to how the fittings mount, angle wise, or take some pictures and bring those too. More info is good when getting something custom made up.