Not sure where you could pick one of those up from pal, but I do know that the Batley Independent Squadbuilder Association (BISSA) have recently released a 'retro' shirt which is similar to the item you are looking for.
For further details check out [urlhttp://www.bissa.co.uk[/url, as far as I know you can purchase on-line. Any proceeds go to the squadbuilder fund.