If you could install a hose over the cable and seal it at the transmission end; while having it extend above the fluid level at the other end, the hose would fill with fluid but it wouldn't leak. The hard part is sealing it at the trans end.
I have used electrical heat shrink tubing with the sealer inside. If you remove the cable from the trans, and remove the adjuster wheel, the tubing will fit over the fitting. Then just apply the heat. Reconnect the cable.
