Why not do a custom one that spans the whole space I have no idea why you would want 2 17” spaces that are pretty useless .BTW IMO a 60” vanity is not large enough for double sinks either

You need a custom built in.

You can do bathroom cabinets the same way you do kitchen ones. You buy two 30" sink bases and a 30" drawer base and two 2.5" filler strips, one for either end. If you don't mind built-in looking cabinets with toe kicks, any home center can help you to configure what you want. See the person in the design center doing semi-custom cabinet design. You can get the bathroom depth cabinets in many or most lines, and people are no longer using 30" or 32" vanities, but are using full height 36" ones in the bath. If you want, you can even do the deeper kitchen style ones and have lots of room to do wall-mount medicine cabinets above them.

I agree, use the whole space. You can have extra storage. If you need ideas, just search the photos for "long vanities." There are tons of ideas, even if you don't want to go custom.

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Or you can do two vanities.

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Lots of options! Have fun!

I even stole the idea of having a narrow pull-out cabinet from kitchen design and had my builder make this for the end of my vanity (custom made to my design).

You can do one with metal round bins to hold hot curling tools, brushes, and combs, too.

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Simply get a 6" wide cab and install this with a door for your vanity attached as the face of it.

Vanities for that space can have lots of configurations. Here is one simple just to fill that space 2-36" vanity base, 1-18" drawer base and fillers on each side. You can use 2-33" vanities and increase the drawer cabinet, etc just too many ways of doing this and everything will depend on need and the look you want. Plenty of room to work with.

Here is a basic layout just to give you an idea.