The best way is the old fashioned way. Buy your self a SB 2 frame or a new gun with a SB 2 frame and send it in for a 357 Magnum barrel. After you get it back rent a reamer, like it was said above under $40 with shipping. That is what I did. A 357 Max can be reamed by you, the 35 Remington needs to be done by a quality gunsmith.
357 Max brass can be hard to find. I think right now is one of those times. Remington has said they are not going to make them any more (the only source). I suspect they will haul out the dies again, if there is enough demand. Unless it is one of the more popular chamberings, brass can be hard to get from time to time. I know for a fact that 375 Win brass was impossible to get about a year and a half ago or so. Now you can buy it most any where. Then last winter 221 Fire Ball brass was no where to be found, again you can find most any where now. I suspect the same thing with 35 Remington there will be times it is difficult to get and others, you can find it every where. 223, 308 and 30-06 are a few examples of cases in stock at all times.
Good Luck and Good Shooting