if you have a welder, even a cheap harbor freight like i do, you can weld up a disk brake mount...
not the prettiest but she works.
also because this is the lowrider thread, heres a pic of my bike when i first built it.
rigid home made front forks, hard to ride at first but not too bad, i ended up commuting 30 miles round trip like this for a good couple weeks till my gf wanted to ride it. i told her not to go too fast till she felt it out but as soon as she turned the corner she went full throttle and lost control. she and the bike were a little tore up but nothing major, in the end i still decided to change up the fork setup.