Ok, the low-buck project is really just a wooden tablet holder that turns my tablet into a chartplotter (EarthNC marine charts works really well on Android).
For about $20 in red oak from Lowes/HD you can make this:
1) 4' length of nominal 1x2 for the "L" brackets (or 1x3 if your tablet has a thick case around it)
2) 2' length of actual 0.5" x 6"
1. measure and cut the back plate, I made mine 1/8" longer than the longest dimension of the tablet - this allows it to slide in and out handily and yet be snug enough not to fall out unexpectedly. For the other dimension I made mine 3/4 higher than the tablet width.
2. Using a router table or table saw, turn the 1x2 into an L-bracket. Cut out a depth of 3/8" (approx half the 1x2 depth), up to 3/8" from the edge.
3. Cut that L bracket into 3 pieces, to fit the sides and bottom of the backplate.
4. Using Titebond III wood glue, glue and clamp the longest piece to the backplate. Make sure the L bracket forms a retaining lip in front of the plate.
5. After that has dried for 12+ hours, clamp and glue the side L brackets forming a retaining lip around 3 sides of the backplate.
6. Drill holes through the side to allow the charging cable to reach the tablet
7. Using forstner bits, drill a "keyhole" to securely hang the holder on a screw mounted in the bulkhead.
8. Sand and varnish.
If you have any questions let me know.