I don't know about your "where to buy?" question. But,I do know what brand to buy. I'm VERY BIASED. But for good reason!! Check it....
Calzone Cases
I truly stand by this brand. I can't say enough about 'em. Great,great stuff. I've had the majority of my Calzone cases for my effects racks,mixing board,cases for all my basses,amps,mics,cables,and cabs since the mid-80's. I've beat'em,bang'em,they've been exposed to more weather than a hooker in a hurricane. Not to mention that the bands I've been in over the decades has moved AT LEAST 2-3 times a month. A few scrapes here & there,but look at it this way...... At the very least,2 moves per month,every month,for OVER 25 years. All the big pro-sound companies use Calzone Cases.
So yeah,they may cost a little more than most. I purchased 90% of'em ALL AT ONCE (Small fortune!!) But I'll be damned if I ain't got my money's worth,for sure!
The old saying is true:"You get what you pay for!"