You haven't looked hard enough
http://www.surplusstore.co.uk/bb-guns/two-tone-bb-pistols/6mm-bb-hfc-glock-17-blue-two-tone-bb-pistol.html
https://bbguns4less.co.uk/products/hfc-ha-117-bb-gun-airsoft-pistol-hand-gun-in-orange.html
Normally I wouldn't recommend cheap springers but in your case, you'll be spending a lot of money on something that you'll only us once or twice. Air rifles will be much cheaper, more reliable and much more accurate than a £60 plastic gbb pistol.
If you're still set on a gas pistol, get an ASG MK23, normally costs around £60, it's accurate, it won't fall apart after afew uses, and if you decide you want to start skirmishing then it's a great side arm. It's a clone of the Marui Mk23.
https://jdairsoft.net/pistol-3/ASG-Mk23-Stealth-Assassin