Yes, the gauges can be purchased through us (Special Edition/Beck), Henry (IM) and also through VDO's largest distributor (N. Hollywood).
The pictured o-ring is just a standard seal and will not fill the gap. You can use a 100mm to 105mm Porsche adapter o-ring, which is common on some 911s and can be purchased from any of the aforementioned vendors. We also offer other custom options for adapting the gauges.
We knew that VDO was going to catalog these gauges, but were told they would still only be available for the 3 previously mentioned sources. I hope that is the case, as we put a lot of time and money into making these...
Regardless, the pricing should be there same across the board and I would encourage anyone looking for these gauges to consider supporting the manufacturers/shops that help keep this industry alive and constantly evolving.