Fitting gauge in a dash

[Memnon]

Not exactly electronics .... but seems best fit sub-forum

I have a dash on a boat, in centre of dash is an oddment tray ... for sunglasses etc.
This is the only free location to fit a 3'5" gauge.

The back of this tray slopes away ... so if I just drilled 3.5" hole the gauge display would not be able to be read.

Pic of dash is here .... https://flic.kr/p/2jcmEfB

My initial though is that I need to make some form of wedge mount, that would make gauge face vertical ...
see my sketch: https://flic.kr/p/2jcpbFA

Alternative options ...
Cut all the back off the oddment tray and fix a flat backplate to it ..... anyone know of a source of quality plastic (nylon ?)
Machining off the back neatly maybe not be easy (unless you know of companies who do this sort of work)


Remove oddment tray entirely and fit a flat blanking plate (might be easiest for fitting)
I guess I could manufacture out of ally sheet ... would need to have some good finish applied (maybe carbon effect foil?)

Suggestions? anybody know of a place that makes prototypes / one off's