The mounting industry does not have an official standard but the AMPS pattern might be as close as you can get (at least for small electronics). The AMPS pattern is a series of four holes aligned in a rectangular pattern. Some manufacturers use two of the four holes while maintaining the AMPS pattern spacing dimensions. The mounting pattern consists of four holes in a rectangular pattern spaced 1.188 inches by 1.813 inches. Some manufacturers also have 2-hole adapters that support the diagonal measurement of 1.912 inches.
The AMPS pattern is fairly well-known in the HAM Radio industry where many head plates from Yaesu and ICOM use this mounting pattern. We find that HAM Radio enthusiasts are pretty handy people and when the mounting pattern doesn’t exist, they don’t mind drilling some holes to match up. These mounts are readily available from several manufacturers. A seat bolt mount with an AMPS plate is a perfect place to park your radio head. Attachment to your seat bolt is a fairly simple operation and typically takes five minutes using a wrench or pliers. Always be sure to wrench tighten the mount to ensure it doesn’t flop to the side.
Garmin and TomTom motorcycle cradles also use the AMPS pattern to attach the custom holder to a mount. Garmin has teamed up with RAM Mounts of late to offer their AMPS Motorcycle Mount for their Zumo series. You will find the holes on this mount line up perfectly with the cradle you received from Garmin. You will need to use the screws and nuts that came from Garmin to attach it to this mount.
Satellite Radios from Sirius/XM use this 4-hole mounting pattern for radios made over the past several years. The back of the powered Sirius cradle has 4 screw holes in the AMPS pattern. The Arkon Suction Cup Mount for Sirius Radio includes a 4-hole plate with screws that fit the back of the cradle perfectly. It even includes an adhesive dash plate to attach the suction to your dash as well as the windshield.
The nice part about the AMPS pattern is these mounts can be used for multiple devices. For example, many of the mounts marketed for Sirius Radio can also be used for a different device that uses this 4-hole pattern. You would need to be sure that the mount is appropriate for the weight and size of the device and you might have to supply different screws and nuts but the pattern is universal in terms of the spacing.
There are a lot of AMPS mount variations available. A great low-priced option is the Arkon Flat Surface Mount. This mount features a ball and socket at the end so the device that is attached can swivel and pivot. The bottom features a sticky surface so it can also attach to a textured dash.
Lastly, consider the RAM Clamp Mount With Double Socket Arm And Round Base Adapter. This one is made of metal and the clamp opens to 1.25 inches. The arm in the middle is three inches long and the mount pivots at the base and the tip. The round adapter at the end not only has the AMPS pattern but it includes several other holes to fit various other electronic mounting patterns. This mount comes with a lifetime warranty.