Sorry for the late post, but if she still needs a SPG, the Scubapro SPG in a brass case is 2.125" in diameter.I gave up trying to find anything. I convinced her to try a Zoop. Will see how it goes.
The Scubapro 2 gauge console w/ the SPG ( 2.125" ) comes w/ an ANALOGUE Depth Gauge 2.5" in diameter.
She could use it as a back up to her dive computer or vise versa.