Can’t offer on where to buy but thought I’d put my $0.02 in and keep up with this thread for a bit.
I was looking to get the ~55 gal tanks but everywhere I found was %50 shipping basically. 2x 55 tanks and 2 sets of the custom straps was over $1000 quote with the shipping. It’s a no go for now.
I looked at the first 4 or 5 “tank vendors” that google came up with and while they all had exactly what I was looking for and were fairly priced for the tanks themselves, again the shipping was truly cost prohibitive.
I think I did find one that had flat rate $100 shipping but since I couldn’t find the cool custom straps unless ordering through the Power Wash store, I decided to table it until a thread popped up on PWR with better information. If I come across that one with the $100 shipping I post the link.
Hoping someone else knows how to get a deal somewhere. Good luck.