You could always try stem bending the shoe molding.

It is not large and might be able to bend tight enough depending on the diameter you need.

I am sort of surprised no one makes something for this.

You could always do a multi-piece mitered joints.

Like a pair of 45 degrees, or a smaller angle and more piece if you want it smother (like three 30 degree pieces for a 90 degree corner).

Flextrim and the like make flexible moulding including shoe moulding.

"Flextrim ..."

no prices show, wonder why?

http://www.youtube.com/watch?v=XwoblSEe7VE

Works with shoe or quarter round molding.

brickeye, they sell thru dealers. There are others out there who sell retail on line I just do not know of them at the moment as I do not work with this type pf product currently and only used them as an example.

If you had some tools (router, bits, bandsaw) you could easily make small radiused corner sections with the profile of base shoe.
Casey

Laminate then shape the corner pieces

If you're turning a 90* corner, and it's basically not safety-critical (like a handrail or something) I would not see the need to laminate it, solid would be fine if you orient the gain properly.
You could fashion one as a pattern, make a mold and cast as many as you needed in resin (think bondo or minwax wood filler)
Casey

You said you had white baseboards installed. If they installed bullnose corner base why can't they do the bullnose shoe?
Ed
thespeedofwood.com