Isolators work with transmitters only. That would do nothing for getting signal from the antenna into the repeaters.
What you need is a diplexer. That is a low pass / high pass filter network. These can be constructed with L/C high pass and low pass filters, but that usually only has enough Q to work with a super wide split, like VHF low pass and UHF high pass. It looks more like you need a pair of interdigital band pass filters. These can be tuned 5 MHz wide so the filter passes both TX and RX and depending on the number of poles will be the isolation, I'd say 5 poles should be around -60dB, 20 MHz out. They are kind of a pain to build as copper is expensive and aluminum is really hard to weld, that aluminum solder crap never worked for me. And then they are a real nutbuster to tune, don't even try it without a spectrum analyzer with a tracking generator. But before you spend any money, I would do a VSWR test with watt meter and a hand held to see if the antenna is broad band enough to support the 2 machines.
