I stumbled across something today that seems to be old news to everyone except those outside Japan.

There is a clothing company in Japan, catering to the bosozoku retro car and motorcycle segment, that has taken the Bellett GT as one of their more favorite graphics or logos.
The names the company uses are "Kamanari69", "Old School Showa Modern" and "Japanese Badboy Kulture".
One of their most popular earlier items (from around 2008?) was a set of dress-wear coveralls, medium blue with white pin stripes, with large embroidered Bellett GT silhouette on the back, and various company logos on the front (parodies of repair shops, tire companies, and car manufacturer logos with the clothing company name in place of the original). These sold for somewhere around $300 USD, and they sold out of the original design with the Bellett. They then made coveralls with several different 1969 era Toyota and Nissan car silhouettes.
Coveralls are apparently the cool thing to wear to car club gatherings and shows, not to work in, more for show.

They seem to have some other items with the Bellett on them, a lower priced solid blue coverall with less elaborate decoration for around $200 USD, shirts for around $90 USD, and hats starting around $60 USD.

I can't find the company website, the links are all dead or wrong. All I find are retailer pages, usually saying the item is sold out, or available only in some tiny size.

Hats and bluejean tag...

Get outta town...they're awesome! Not much available for 6ft tall Aussies I'd imagine.

I keep picking at this and finding more.

It looks like the product line might be under an umbrella company called Ted's Company Lucky Clothing, or Tedman's.
http://www.tedman.co.jp/
The Kaminari stuff is at:
http://www.tedman.co.jp/index_kaminari.html
This seems to explain why there are links to a dead domain name... They started out independent and got swallowed up by a bigger fish.

They show the Bellett GT coveralls completely sold out in all sizes.
Look under the Other button that has "その他" written under it.
The Bellett GT jacket shows it is also sold out in all sizes.
Look under the Other button that has "アウター" written under it.
Those are the only two I see which use that design.
So any chance of finding something with the Bellett GT would be finding it sitting on a shelf in a shop somewhere.

As far as sizes go, the Japanese letter sizes run a size or a size-and-a-half smaller than western sizes.
A Japanese Large would be for a 5'4" - 5'7" healthy person. About a western Medium or a tight Medium.
A Japanese XL is a tight western Large - 5'10"-5'11" healthy person.
And they don't show any charts with XXL or XXXL sizes.

I would need one to fit a Sumo Wrestler

Cool find - better to find out that they had them and they are sold out than that they never existed at all!

The Japanese!!! Cool but different! Always!