I found this GI Joe VAMP at Target in the US a few weeks ago. JADA is the manufacturer.
Here is a size comparison with a Warlord Bolt Action GI. It looks pretty close to scale to me.
Also a scale picture with the original.
The box says there is also a HISS Tank with Destro available. I've seen many awesome threads with 28MM GI Joe, hopefully this is helpful.
Kaluthmar