There are not a lot of variations in microphone impedances for VHF radios, mostly just different connectivity. If yours has a connector that can be dismantled and the "pinout" copied when adding a different mike (usually there is a PTT line a mic line a common line and a shield line connection, perhaps one other if the PTT and mic do not share a common). If there is not a connector and the mic itself can be dismantled so that you can "Ohm-out" the mic, PTT etc. parts to the ends of the wires you can then copy a different color coded mic cord and solder it in.
Even without being concerned about the mic impedance it is usually worth your while to get a "universal replacement" mic or some other one available in some surplus supply and try it. A used mic should not cost more than about five bucks.