Black water tank gauge

[T&JClower]

We have a new-to-us R27 2018 model. Does not have a black water tank gauge. Would like to add one but the black water tank does not seem to be practically accessible. Is there a trick or a preferred approach for adding a black water tank gauge. Thanks!

 

[Bruce Moore]

Bumping post delayed in moderation queue.

 

[Mastercraft]

I have a 2017 R29. I just hooked up a SCAD TM1 gauge that sticks on black water tank. I am not sure how good it is since I have not filled tank yet. I think it is on amazon and fisheries supply. Not cheap, $175.
Do you have an led light on your flushing switch? LED is green when empty, yellow, half, red full.