there are a couple ways to do it.
1) put a 3 dB attenuator in between the two filters. that way bounce back signals are 6 dB less (3 db one way, and 3 dB coming back) and you might be able to live with the loss
2) build a diplexer filter so that out of band signals to a different port (which you would terminate in 50 ohm load). the theory behind it is to make a bandpass and bandstop filter, connected together at a juncion, but instead of a "chebychev" or a "max flat" design, you would use a "singly terminated" design. In narrow band applications, you can just get away with the two filters and some sort of reactance canceling element near the junction
3) use a ferrite isolator in between the two filters (we used to use them all the time, back in the day, but seldom do now due to the added expense)