There was loads on eBay a while back, got mine for £28. Edit, still some there https://www.ebay.co.uk/itm/SureFire-Sidekick-300-Lumen-Ultra-Compact-Triple-Output-Keychain-Light-Black/372853474425?hash=item56cfcc8479:g:2NsAAOSwE21dP7hl
Guy has some negative feedback for fake stuff. Plus considerably cheaper than other places. I'd be weary tbh.
Edit, still some there https://www.ebay.co.uk/itm/SureFire-Sidekick-300-Lumen-Ultra-Compact-Triple-Output-Keychain-Light-Black/372853474425?hash=item56cfcc8479:g:2NsAAOSwE21dP7hl