Here is the link http://www.qsps.com.tw/page/product/show.aspx?num=107&kind=70&page=1&lang=US
Can be used for rd400 daytona.
while they are interesting, they arent that good. those have been around for years for rds. neat though.
If it is mechanical, it surely cannot work on a tank with the cap on the centerline?
the old ones had a float that tied to a chain that worked against a spring in the cap. which if you acelerated hard would sling back and th enedle would bounce all over the place. I had a few. they were 'ok' when sitting still but? bike has to be upright and basically not moving.
Definitely sounds useless. I mostly reset the trip counter on my bikes when refueling. With a reserve type petcock, I hardly see the need for a fuel level gauge.
About 10-15 years ago the vintage NOS ones were going for huge money, a couple hundred each.