Dreamforge has just launched a kickstarter for a Grav Stug tank -
link$49 for one. They're shipping direct from Hong Kong, so expect to be hit with import duties. p&p estimates are at the bottom of the page, but look to average around $6 for a single model.
There are a number of barrel options (not so keen on the short version, but some of the longer ones look promising)
Just launched today, runs until April 17, with delivery August, September time (seems the more you want the longer you wait
)
edited to update post title