When I say custom make I mean on some website

If it's possible that would be amazing

Just get a slimline fixture and some RDC lamp holders. One fixed and one plunger for each bulb. Gut the slimline and install the sockets and the VHO ballast.

Like FGS said, and if you fire a PM to vytautas_lamps they might give you some tips on making the hardest part of that setup, the Powergrove tubes, take a look at his gallery HERE, really he has made his own with nothing more then a gas stove in his kitchen altering factory made tubes.  

@FGS:
A slimline fixture isn't deep enough to fit a VHO ballast in.
Needs to be a HO or VHO fixture.

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@F96T12 DD VHO:
You could always get some sheetmetal & build your own (unless you're talking something more than 4-feet..)