Cheap source for large propane tanks?

Hi folks, I'd like to start with building a TLUD gasifier, to utilise the heat, and biochar.
Any ideas on where might be good places to source some cheap large propane tanks say around 100lb or 45kg tanks?
Thanks
Mat

I buy them at Home Depot or Lowes new for $135. You can also go to propane suppliers and ask to buy their scrap metal, which is tanks cut in half. Tanks have to be decommissioned so there is a steady supply, but they aren't used to people trying to buy them, so focus on them as scrap metal and not as tanks.

Thanks for the reply

Generally from my experience in Australia we don't buy the large tanks, they are hired from the gas company, so buying new may prove a challenge, but I will look around.

I will definitely try and find some propane tank suppliers nearby. If I can get them at scrap prices, then just weld them back together I will be a happy man

I built myself a proof of concept TLUD gasifier from 2 x 5L pertol cans.
Working on a larger system using 5kg and 9kg gas cylinders - cut the tops and bottoms off and welded them together to make a larger cylinder, but it's a lot of cutting and welding (although I need the welding experience!)

Thanks again.

Mat