Where can i buy a cheap gl tank that isnt second hand?

im in the UK and when you see videos on youtube of people with 3 foot gl tanks they say " i picked this up at petco/ petsmart etc... for $20" in the uk all i can find is aquariums that are made by top companys like juwel and rena that are like 300 pound for a 3 foot tank, where can i just get a cheap gl tank suitable for 2-3 leopard geckos?