Look on ebay for a vhf cavity filter. One cavity will do it. It's going to be about two feet long, and 4-8 inches in diameter. What you want can't be done in a small package. But VHF cavities can be had cheap. Even a pass cavity can be pressed into service as a notch, if you know what you're doing. But it's quite possible to notch out the weather transmitter without taking a significant hit in performance on the railroad frequencies. But, like I said, the filter will be LARGE!
Another possibility is to use a small yagi, like 3 elements, aim it AWAY from the weather transmitter, and take what you can get on the railroad stuff. A small yagi isn't so directional that you won't hear stuff off the sides and back. It'll work ok, but it might reduce the weather station enough that it's not so much of a problem.
A question that has to be asked... do you use a preamp? If so, lose it! I ask because I live in an area with multiple strong VHF weather transmitters, and lots of paging, and there is zero overload. I also use a unity gain antenna and no preamp.