RS485 describes a 120 ohm resistor IIANM , what happens if you put in a larger value say 1k or 10k ?
The impedance changes but is it not better to have something than nothing ?
With a much higher resistance as you said the reflection would still be there, like 90% for the 1k and 99% for the 10k, so not helping much...
Even if the round trip is much shorter than the bit period, you left the receiver end with 10k, you have a reflection of 99% when it finds the receiver, then, when it finds the transmitter you have a reflection of the same amplitude in the opposite direction and this goes back and starts again. The thing takes a while to extinguish and you might encounter problems. You could try out and find what's going on, probe the line and see what happens at both ends.
If one is transmitting and one receiving you could increase the termination and the source resistance by adding a series resistor to the source output, if both are transmitting and receiving this won't work as now you have a series resistor to the receiver and signal amplitude would be low.